This is a presentation i made about Denial of Service or a Distributed Denial of Service (DoS / DDoS) and the latest methods used to crash anything online and the future of such attacks which can disrupt the whole internet . Such attacks which are in TB's and can be launched from just single computer. And, there is not much that can be done to prevent them.
This document discusses distributed denial of service (DDoS) attacks. It begins by defining a DDoS attack as an attempt to make an online service unavailable by overwhelming it with traffic from multiple sources. It then explains how DDoS attacks work by exploiting vulnerable systems to create large networks of compromised devices that can be directed by an attacker to target a specific system or server. Finally, it discusses different types of DDoS attacks including volumetric attacks, protocol attacks, and application layer attacks and some famous DDoS incidents like attacks on the Church of Scientology and various websites.
DDOs Attacks (Distributed Denial of Service
Attacks
DoS Basics
What is Internet?
What resources you access through Internet?
Who uses those resources?
Good vs Bad Users
Denial-of-Service attack
-DoS attack is a malicious attempt by a single person or a group of people to cause the victim, site, or node to deny service to its customers.
-What is (DoS)Attack
An attack that attempts to stop or prevent a legitimate user from accessing a service or system. The attacker will either directly attack the users network or system or the system or service that the users are attempting to access.
-Distributed denial of service attack (DDoS)
This type of attack is distributed among many different systems making it more powerful and harder to shutdown
This document discusses distributed denial of service (DDoS) attacks. It begins with an introduction that defines denial of service (DoS) attacks and how DDoS attacks differ in employing multiple compromised computers to coordinate a widespread attack. It then provides examples of targets that can be affected and overviews how DDoS attacks work by flooding the victim with traffic from many sources. The document goes on to discuss specific DDoS attack types, defenses against attacks, and how attacks are practically handled through router filtering, black hole routing, and traffic diversion techniques.
This document provides an overview of distributed denial of service (DDoS) attacks. It discusses the components and architecture of DDoS attacks and classifies them into four categories: flood attacks, amplification attacks, TCP SYN attacks, and malformed packet attacks. Specific attack types like UDP floods, ICMP floods, Smurf attacks and Fraggle attacks are described. The document also covers DDoS defense problems and classifications such as intrusion prevention, detection, tolerance and response. It concludes that DDoS attacks are difficult to prevent due to readily available tools and the ability to target any internet host, and that the best defense involves vigilant system administration.
This document provides information about different types of denial of service (DoS) and distributed denial of service (DDoS) attacks, including buffer overflow, ping of death, smurf attack, and TCP SYN attack. It explains that DoS attacks aim to make machines or network resources unavailable by overwhelming them with more requests than their capacity allows. DDoS attacks perform the same type of flooding from multiple sources rather than a single source. The document also discusses how buffer overflows can corrupt data and crash systems, how ping of death exploits IP fragmentation, and how smurf attacks work by amplifying traffic volume through IP broadcast replies.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as an attack that seeks to oversaturate a targeted machine's capacity to disrupt authorized use, while a DDoS uses multiple compromised systems to flood the target. The document describes how DDoS attacks work by flooding the victim from many sources, making it hard to block. It lists common DoS attacks like buffer overflow and ICMP floods, and DDoS attack types like traffic floods and application attacks. The document also covers typical attacker motivations and recommendations to prevent attacks like buying more bandwidth and building redundancy.
This is a presentation i made about Denial of Service or a Distributed Denial of Service (DoS / DDoS) and the latest methods used to crash anything online and the future of such attacks which can disrupt the whole internet . Such attacks which are in TB's and can be launched from just single computer. And, there is not much that can be done to prevent them.
This document discusses distributed denial of service (DDoS) attacks. It begins by defining a DDoS attack as an attempt to make an online service unavailable by overwhelming it with traffic from multiple sources. It then explains how DDoS attacks work by exploiting vulnerable systems to create large networks of compromised devices that can be directed by an attacker to target a specific system or server. Finally, it discusses different types of DDoS attacks including volumetric attacks, protocol attacks, and application layer attacks and some famous DDoS incidents like attacks on the Church of Scientology and various websites.
DDOs Attacks (Distributed Denial of Service
Attacks
DoS Basics
What is Internet?
What resources you access through Internet?
Who uses those resources?
Good vs Bad Users
Denial-of-Service attack
-DoS attack is a malicious attempt by a single person or a group of people to cause the victim, site, or node to deny service to its customers.
-What is (DoS)Attack
An attack that attempts to stop or prevent a legitimate user from accessing a service or system. The attacker will either directly attack the users network or system or the system or service that the users are attempting to access.
-Distributed denial of service attack (DDoS)
This type of attack is distributed among many different systems making it more powerful and harder to shutdown
This document discusses distributed denial of service (DDoS) attacks. It begins with an introduction that defines denial of service (DoS) attacks and how DDoS attacks differ in employing multiple compromised computers to coordinate a widespread attack. It then provides examples of targets that can be affected and overviews how DDoS attacks work by flooding the victim with traffic from many sources. The document goes on to discuss specific DDoS attack types, defenses against attacks, and how attacks are practically handled through router filtering, black hole routing, and traffic diversion techniques.
This document provides an overview of distributed denial of service (DDoS) attacks. It discusses the components and architecture of DDoS attacks and classifies them into four categories: flood attacks, amplification attacks, TCP SYN attacks, and malformed packet attacks. Specific attack types like UDP floods, ICMP floods, Smurf attacks and Fraggle attacks are described. The document also covers DDoS defense problems and classifications such as intrusion prevention, detection, tolerance and response. It concludes that DDoS attacks are difficult to prevent due to readily available tools and the ability to target any internet host, and that the best defense involves vigilant system administration.
This document provides information about different types of denial of service (DoS) and distributed denial of service (DDoS) attacks, including buffer overflow, ping of death, smurf attack, and TCP SYN attack. It explains that DoS attacks aim to make machines or network resources unavailable by overwhelming them with more requests than their capacity allows. DDoS attacks perform the same type of flooding from multiple sources rather than a single source. The document also discusses how buffer overflows can corrupt data and crash systems, how ping of death exploits IP fragmentation, and how smurf attacks work by amplifying traffic volume through IP broadcast replies.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as an attack that seeks to oversaturate a targeted machine's capacity to disrupt authorized use, while a DDoS uses multiple compromised systems to flood the target. The document describes how DDoS attacks work by flooding the victim from many sources, making it hard to block. It lists common DoS attacks like buffer overflow and ICMP floods, and DDoS attack types like traffic floods and application attacks. The document also covers typical attacker motivations and recommendations to prevent attacks like buying more bandwidth and building redundancy.
This document provides an overview of intrusion detection systems (IDS). It begins with an introduction that defines intrusion, intrusion detection, and IDS. It then discusses the history and typical scenarios of intrusions. The document outlines different types of attacks and what an IDS is supposed to do in detecting them. It classifies IDS based on detection approach and protected system, covering network/host-based detection. The advantages and disadvantages of different IDS types are presented. Commonly used open source and commercial IDS are listed, with Snort discussed in more detail. References for further information are provided at the end.
An introduction to denial of service attacksRollingsherman
The document discusses denial of service (DoS) attacks, which are common and costly. It describes different types of DoS attacks like distributed denial of service (DDoS) and SYN floods. The document outlines symptoms of DoS attacks and steps users can take to prevent becoming part of a botnet. It also discusses the legal issues around DoS attacks and how some governments use them against other governments.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS attacks as attempts to render a system unusable or slow it down for legitimate users by overloading its resources. DDoS attacks multiply the effectiveness of DoS by using multiple compromised computers to launch attacks simultaneously. Common DoS attack types like SYN floods, Smurf attacks, and ping of death are described. The rise of botnets, which are networks of compromised computers controlled remotely, enabled more powerful DDoS attacks. Mitigation strategies include load balancing, throttling traffic, and using honeypots to gather attacker information.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as making a machine or network unavailable to its intended users. DDoS uses other computers to launch the attack. Methods of attack mentioned include ICMP floods, teardrop attacks, and reflected/spoofed attacks. Signs of an attack include slow network performance. The document provides tips for system administrators and users, such as contacting providers and following security best practices, to mitigate attacks.
The document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as an attack that renders a system unable to provide normal services by flooding it with traffic. DDoS uses multiple compromised systems to launch a coordinated DoS attack against one or more targets, multiplying the attack effectiveness. Attacks are classified by the system targeted (clients, routers, firewalls, servers), part of the system (hardware, OS, TCP/IP stack), and whether they exploit bugs or just overload resources. Common DDoS tools like Trinoo and TFN are mentioned. Protection from these large-scale attacks remains a challenge.
A DOS attack is designed to deny legitimate users access to a resource by overwhelming it with requests. There are two main types: a basic DOS attack from a single host, and a distributed DOS (DDOS) attack from multiple compromised machines targeting the same victim. To prevent DOS attacks, organizations can install security patches, use intrusion detection systems to identify illegal activities, configure firewalls to block traffic from attackers, and use access control lists on routers to limit network access and drop suspicious traffic.
DDoS attacks target companies and institutions that provide online services. They work by overloading servers with traffic from multiple compromised systems known as "bots" or "zombies". Common DDoS attack types include SMURF, TCP SYN/ACK, UDP flood, DNS amplification, and attacks using peer-to-peer networks. Defenses include configuring routers and firewalls to filter unauthorized traffic, limiting response messages, and tracking malicious activity on peer-to-peer networks. As attack methods evolve, continued development of detection and mitigation techniques is needed.
Web application attacks can take many forms, including cross-site scripting (XSS), SQL injection, parameter tampering, command injection, session management issues, cookie poisoning, directory traversal, cross-site request forgery, and buffer overflows. XSS is a vulnerability that allows malicious JavaScript code to be injected and run in a user's browser, potentially accessing data. SQL injection involves inserting SQL commands into a database query to gain unauthorized access. Parameter tampering modifies URL parameters to change expected behavior.
Understand AWS best practices for Distributed Denial of Service (DDoS) resiliency and how AWS Shield can assist you to protect your business. Uncover how this tool safeguards web applications running on AWS, and how always-on detection and automatic inline mitigations minimize application downtime and latency.
This document discusses threat modeling for software applications. It covers the key stages of threat modeling including decomposing the application, determining and ranking threats using STRIDE, and determining countermeasures. Specific topics covered include threat modeling approaches, data flow diagrams, trust levels, the STRIDE framework for analyzing spoofing, tampering, repudiation, information disclosure, denial of service, and elevation of privilege threats. It also discusses mobile threat modeling and provides an example threat analysis of a student results portal application.
Penetration testing is used to test the security of a website by simulating real attacks from outside. It identifies potential vulnerabilities to prevent harmful attacks. By understanding how attacks work, the IT team can fix issues and prevent larger attacks in the future. The presentation will demonstrate a penetration testing tool that checks the login page for security issues like authentication, redirects, and hidden code. Contact information is provided for any additional questions.
This document discusses DNS spoofing attacks. It defines DNS as the internet's equivalent of a phone book that translates domain names to IP addresses. It describes several types of DNS attacks including denial of service attacks and DNS amplification attacks. It explains how DNS spoofing works by introducing corrupt DNS data that causes the name server to return an incorrect IP address, diverting traffic to the attacker. The document also discusses ways to prevent DNS spoofing such as using DNSSEC to add cryptographic signatures to DNS records and verifying responses.
Introduction to Web Application Penetration TestingAnurag Srivastava
Web Application Pentesting
* Process to check and penetrate the security of a web application or a website
* process involves an active analysis of the application for any weaknesses, technical flaws, or vulnerabilities
* Any security issues that are found will be presented to the system owner, together with an assessment of the impact, a proposal for mitigation or a technical solution.
Cross Site Scripting (XSS) is a vulnerability that allows malicious users to insert client-side code into web pages that is then executed by a user's browser. This code can steal cookies, access private information, perform actions on the user's behalf, and redirect them to malicious websites. XSS works by having the server display input containing malicious JavaScript from a request. There are different types of XSS attacks, including non-persistent, persistent, and DOM-based attacks. Prevention methods include validating, sanitizing, and escaping all user input on the server-side and client-side. Web vulnerability scanners like Burp Suite can help test for XSS and other vulnerabilities.
DDoS Attack Detection & Mitigation in SDNChao Chen
This document summarizes a presentation on detecting and mitigating distributed denial of service (DDoS) attacks in software-defined networks. It discusses using sFlow and the Floodlight controller to detect common DDoS attack types like ICMP floods, SYN floods, and DNS amplification. An application was developed in Python to classify attacks and push static flow entries to direct attack traffic to the sFlow collector for analysis. The scheme was tested in a Mininet virtual network and shown to successfully mitigate ICMP and SYN flood attacks. Future work includes testing DNS amplification and UDP floods, implementing adaptive sampling rates and thresholds, and designing an unblocking mechanism.
Intrusion Detection Systems and Intrusion Prevention Systems Cleverence Kombe
Intrusion detection system (IDS) is software that automates the intrusion detection process. The primary responsibility of an IDS is to detect unwanted and malicious activities. Intrusion prevention system (IPS) is software that has all the capabilities of an intrusion detection system and can also attempt to stop possible incidents.
This document discusses a denial of service (DoS) attack. It describes DoS attacks as flooding a server with data packets to create heavy internet traffic and deny service to legitimate users. It outlines the tools needed to perform a DoS attack, including a Linux machine, Mono, Mono-gmcs, and LOIC. It then explains the methodology, describing how to specify the target URL in LOIC and set it to UDP mode to flood packets without acknowledgment. Finally, it discusses the pros and cons of DoS attacks, noting they damage servers and reputation while allowing attackers to remain untraced.
Aleksei zaitchenkov slides about DOS AttacksDipesh Karade
This document discusses denial of service (DoS) attacks. It begins with definitions of DoS and DDoS attacks, then discusses the history of major attacks including the Morris Worm in 1988 and the SQL Slammer worm in 2003. It outlines different types of DoS attacks such as flooding, penetration, eavesdropping, and man-in-the-middle attacks. Major targets of attacks are also discussed, including the 2007 cyberattacks against Estonia. The document concludes with methods of defense against DoS attacks and challenges around their prosecution.
DOS / DDOS introduction
How Easy it is to get information
Real Life Examples MyDoom , GitHub , Dyn , Windows Server and Windows 10 servers running Internet Information Services (IIS) are vulnerable to denial of service (DOS) attacks
Base of Attacks
Types of DOS / DDOS
Attack Tools , LOIC, XOIC, Stacheldracht
DOS/DDOS Weaknesses
Category of OS/ DDOS
What to defend?
Botnets and Botnets mitigations
Michael Calce, a.k.a. MafiaBoy
Point of entrance / OSI Model ( If time permit)
This document provides an overview of intrusion detection systems (IDS). It begins with an introduction that defines intrusion, intrusion detection, and IDS. It then discusses the history and typical scenarios of intrusions. The document outlines different types of attacks and what an IDS is supposed to do in detecting them. It classifies IDS based on detection approach and protected system, covering network/host-based detection. The advantages and disadvantages of different IDS types are presented. Commonly used open source and commercial IDS are listed, with Snort discussed in more detail. References for further information are provided at the end.
An introduction to denial of service attacksRollingsherman
The document discusses denial of service (DoS) attacks, which are common and costly. It describes different types of DoS attacks like distributed denial of service (DDoS) and SYN floods. The document outlines symptoms of DoS attacks and steps users can take to prevent becoming part of a botnet. It also discusses the legal issues around DoS attacks and how some governments use them against other governments.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS attacks as attempts to render a system unusable or slow it down for legitimate users by overloading its resources. DDoS attacks multiply the effectiveness of DoS by using multiple compromised computers to launch attacks simultaneously. Common DoS attack types like SYN floods, Smurf attacks, and ping of death are described. The rise of botnets, which are networks of compromised computers controlled remotely, enabled more powerful DDoS attacks. Mitigation strategies include load balancing, throttling traffic, and using honeypots to gather attacker information.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as making a machine or network unavailable to its intended users. DDoS uses other computers to launch the attack. Methods of attack mentioned include ICMP floods, teardrop attacks, and reflected/spoofed attacks. Signs of an attack include slow network performance. The document provides tips for system administrators and users, such as contacting providers and following security best practices, to mitigate attacks.
The document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as an attack that renders a system unable to provide normal services by flooding it with traffic. DDoS uses multiple compromised systems to launch a coordinated DoS attack against one or more targets, multiplying the attack effectiveness. Attacks are classified by the system targeted (clients, routers, firewalls, servers), part of the system (hardware, OS, TCP/IP stack), and whether they exploit bugs or just overload resources. Common DDoS tools like Trinoo and TFN are mentioned. Protection from these large-scale attacks remains a challenge.
A DOS attack is designed to deny legitimate users access to a resource by overwhelming it with requests. There are two main types: a basic DOS attack from a single host, and a distributed DOS (DDOS) attack from multiple compromised machines targeting the same victim. To prevent DOS attacks, organizations can install security patches, use intrusion detection systems to identify illegal activities, configure firewalls to block traffic from attackers, and use access control lists on routers to limit network access and drop suspicious traffic.
DDoS attacks target companies and institutions that provide online services. They work by overloading servers with traffic from multiple compromised systems known as "bots" or "zombies". Common DDoS attack types include SMURF, TCP SYN/ACK, UDP flood, DNS amplification, and attacks using peer-to-peer networks. Defenses include configuring routers and firewalls to filter unauthorized traffic, limiting response messages, and tracking malicious activity on peer-to-peer networks. As attack methods evolve, continued development of detection and mitigation techniques is needed.
Web application attacks can take many forms, including cross-site scripting (XSS), SQL injection, parameter tampering, command injection, session management issues, cookie poisoning, directory traversal, cross-site request forgery, and buffer overflows. XSS is a vulnerability that allows malicious JavaScript code to be injected and run in a user's browser, potentially accessing data. SQL injection involves inserting SQL commands into a database query to gain unauthorized access. Parameter tampering modifies URL parameters to change expected behavior.
Understand AWS best practices for Distributed Denial of Service (DDoS) resiliency and how AWS Shield can assist you to protect your business. Uncover how this tool safeguards web applications running on AWS, and how always-on detection and automatic inline mitigations minimize application downtime and latency.
This document discusses threat modeling for software applications. It covers the key stages of threat modeling including decomposing the application, determining and ranking threats using STRIDE, and determining countermeasures. Specific topics covered include threat modeling approaches, data flow diagrams, trust levels, the STRIDE framework for analyzing spoofing, tampering, repudiation, information disclosure, denial of service, and elevation of privilege threats. It also discusses mobile threat modeling and provides an example threat analysis of a student results portal application.
Penetration testing is used to test the security of a website by simulating real attacks from outside. It identifies potential vulnerabilities to prevent harmful attacks. By understanding how attacks work, the IT team can fix issues and prevent larger attacks in the future. The presentation will demonstrate a penetration testing tool that checks the login page for security issues like authentication, redirects, and hidden code. Contact information is provided for any additional questions.
This document discusses DNS spoofing attacks. It defines DNS as the internet's equivalent of a phone book that translates domain names to IP addresses. It describes several types of DNS attacks including denial of service attacks and DNS amplification attacks. It explains how DNS spoofing works by introducing corrupt DNS data that causes the name server to return an incorrect IP address, diverting traffic to the attacker. The document also discusses ways to prevent DNS spoofing such as using DNSSEC to add cryptographic signatures to DNS records and verifying responses.
Introduction to Web Application Penetration TestingAnurag Srivastava
Web Application Pentesting
* Process to check and penetrate the security of a web application or a website
* process involves an active analysis of the application for any weaknesses, technical flaws, or vulnerabilities
* Any security issues that are found will be presented to the system owner, together with an assessment of the impact, a proposal for mitigation or a technical solution.
Cross Site Scripting (XSS) is a vulnerability that allows malicious users to insert client-side code into web pages that is then executed by a user's browser. This code can steal cookies, access private information, perform actions on the user's behalf, and redirect them to malicious websites. XSS works by having the server display input containing malicious JavaScript from a request. There are different types of XSS attacks, including non-persistent, persistent, and DOM-based attacks. Prevention methods include validating, sanitizing, and escaping all user input on the server-side and client-side. Web vulnerability scanners like Burp Suite can help test for XSS and other vulnerabilities.
DDoS Attack Detection & Mitigation in SDNChao Chen
This document summarizes a presentation on detecting and mitigating distributed denial of service (DDoS) attacks in software-defined networks. It discusses using sFlow and the Floodlight controller to detect common DDoS attack types like ICMP floods, SYN floods, and DNS amplification. An application was developed in Python to classify attacks and push static flow entries to direct attack traffic to the sFlow collector for analysis. The scheme was tested in a Mininet virtual network and shown to successfully mitigate ICMP and SYN flood attacks. Future work includes testing DNS amplification and UDP floods, implementing adaptive sampling rates and thresholds, and designing an unblocking mechanism.
Intrusion Detection Systems and Intrusion Prevention Systems Cleverence Kombe
Intrusion detection system (IDS) is software that automates the intrusion detection process. The primary responsibility of an IDS is to detect unwanted and malicious activities. Intrusion prevention system (IPS) is software that has all the capabilities of an intrusion detection system and can also attempt to stop possible incidents.
This document discusses a denial of service (DoS) attack. It describes DoS attacks as flooding a server with data packets to create heavy internet traffic and deny service to legitimate users. It outlines the tools needed to perform a DoS attack, including a Linux machine, Mono, Mono-gmcs, and LOIC. It then explains the methodology, describing how to specify the target URL in LOIC and set it to UDP mode to flood packets without acknowledgment. Finally, it discusses the pros and cons of DoS attacks, noting they damage servers and reputation while allowing attackers to remain untraced.
Aleksei zaitchenkov slides about DOS AttacksDipesh Karade
This document discusses denial of service (DoS) attacks. It begins with definitions of DoS and DDoS attacks, then discusses the history of major attacks including the Morris Worm in 1988 and the SQL Slammer worm in 2003. It outlines different types of DoS attacks such as flooding, penetration, eavesdropping, and man-in-the-middle attacks. Major targets of attacks are also discussed, including the 2007 cyberattacks against Estonia. The document concludes with methods of defense against DoS attacks and challenges around their prosecution.
DOS / DDOS introduction
How Easy it is to get information
Real Life Examples MyDoom , GitHub , Dyn , Windows Server and Windows 10 servers running Internet Information Services (IIS) are vulnerable to denial of service (DOS) attacks
Base of Attacks
Types of DOS / DDOS
Attack Tools , LOIC, XOIC, Stacheldracht
DOS/DDOS Weaknesses
Category of OS/ DDOS
What to defend?
Botnets and Botnets mitigations
Michael Calce, a.k.a. MafiaBoy
Point of entrance / OSI Model ( If time permit)
denialofservice.pdfdos attacck basic details with interactive designperfetbyedshareen
The document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS attacks as attempts to render a system unusable or slow it down for legitimate users by overloading its resources. DDoS attacks multiply the effectiveness of DoS by using multiple compromised computers to launch attacks simultaneously. Common DoS attack types like SYN floods, smurf attacks, and ping of death are described. The rise of botnets, which are networks of compromised computers controlled remotely, enable large-scale DDoS attacks that are difficult to defend against. Ways to mitigate DDoS attacks include load balancing, throttling incoming traffic, and using honeypots to gather attacker information.
1. Trapdoors are secret entry points into a system that bypass normal security procedures, commonly used by developers in compilers. Logic bombs are malicious programs that are triggered when specified conditions are met, such as a particular date or user, and typically damage the system.
2. Trojan horses appear to have a normal function but have hidden malicious effects that violate security policies. Viruses are self-replicating code that alters normal programs to include infected versions and can have hidden payloads.
3. Worms propagate fully functioning copies of themselves across networks to infect other computers. Notable worms include Morris, Code Red, Nimda, Slammer, and Conficker which exploited software vulnerabilities to spread rapidly and
This document provides an overview of denial of service (DoS) attacks, including categories and types. It discusses direct DoS attacks such as single-tier, dual-tier, and triple-tier distributed attacks. Indirect DoS attacks through viruses and worms are also covered. The document concludes with strategies for preventing DoS attacks, such as following security best practices, implementing intrusion detection, and coordinating with internet service providers.
This document discusses denial of service (DoS) attacks, including their history and types. It explains that a DoS attack is a malicious attempt to deny service to customers of a target site or network. The first major DoS attack was the 1988 Morris Worm, which infected 10% of internet computers and cost millions to clean up. Common types of DoS attacks are penetration attacks, eavesdropping, man-in-the-middle attacks, and flooding attacks, which overwhelm a target with traffic. While nothing can entirely prevent DoS attacks, defenses include firewalls, routers, switches, bandwidth limitations, and keeping systems patched. The document concludes that future DoS attacks may aim for broad destabilization rather
CS101- Introduction to Computing- Lecture 39Bilal Ahmed
Cyber crime takes many forms such as denial of service attacks, software piracy, viruses, and industrial espionage. DoS attacks involve overloading servers with traffic to render them unusable. Viruses are self-replicating software that infect files and systems. Common defenses include email filtering, intrusion detection, encryption, and antivirus software. Engaging in cyber crimes can result in legal prosecution with jail time and fines.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
This document discusses information security and denial of service (DoS) attacks. It begins with an agenda on information security incident handling. It then defines DoS attacks and explains they are aimed at availability, not confidentiality or integrity. It describes different types of DoS attacks including distributed denial of service (DDoS) attacks. The document outlines detection and analysis of DoS attacks as well as containment, eradication, recovery, and post-incident activities. It concludes with ways employees can help maintain network security.
This document discusses various types of cyber attacks and threats such as viruses, worms, Trojan horses, botnets, trap doors, logic bombs, denial of service attacks, and spyware. It provides details on the characteristics and techniques of different attacks, including how viruses, worms, and Trojan horses infect systems. Distributed denial of service (DDoS) attacks are explained along with specific DDoS techniques like SYN floods and Smurf attacks. The document is a lecture on cryptography and network security that outlines different cyber threats.
This document discusses denial of service (DoS) attacks. It provides a brief history of DoS attacks, including the Morris Worm in 1988 and the SQL Slammer worm in 2003. These early attacks demonstrated how rapidly DoS malware could spread through networks and bring infrastructure to a halt. The document outlines different types of DoS attacks such as penetration tests, eavesdropping, man-in-the-middle attacks, and flooding. Common targets today and defenses against DoS attacks like firewalls and routers are also mentioned. The conclusion discusses how international boundaries complicate law enforcement against DoS attackers and how future attacks may aim to broadly destabilize networks rather than target specific sites.
A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer resource unavailable to its intended users. Although the means to carry out, motives for, and targets of a DoS attack may vary, it generally consists of the concerted efforts of a person or people to prevent an Internet site or service from functioning efficiently or at all, temporarily or indefinitely. Perpetrators of DoS attacks typically target sites or services hosted on high-profile web servers such as banks, credit card payment gateways, and even root name servers. The term is generally used with regards to computer networks, but is not limited to this field, for example, it is also used in reference to CPU resource management. There are two general forms of Dos attacks: those that crash services and those that flood services.
One common method of attack involves saturating the target machine with external communications requests, such that it cannot respond to legitimate traffic, or responds so slowly as to be rendered effectively unavailable. In general terms, DoS attacks are implemented by either forcing the targeted computer to reset, or consuming its resources so that it can no longer provide its intended service or obstructing the communication media between the intended users and the victim so that they can no longer communicate adequately.
This document provides an overview of several cybersecurity topics:
- Botnets, which are networks of compromised computers controlled remotely. They are used to launch DDoS attacks, send spam, and other malicious activities.
- Watering hole attacks target specific groups by infecting websites they commonly visit.
- Spear phishing attacks use targeted emails to steal sensitive information.
- DDoS attacks overwhelm servers with traffic from multiple compromised systems. Detection and prevention methods are discussed for each topic.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS as an attempt to make a machine or network unavailable to its intended users. A DDoS attack involves using multiple compromised systems to launch a DoS attack on a single target. Types of DDoS attacks include bandwidth attacks, SYN flood attacks, and program/application attacks. The document also discusses botnets, common DDoS attack tools like Hulk, symptoms of a DoS attack, and various countermeasures organizations can implement such as IDS/IPS, firewalls, ingress/egress filtering, and load balancing to detect and mitigate DDoS attacks.
This document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS attacks as attempts to make a machine or network resource unavailable to its intended users, and notes that they aim to prevent legitimate users from accessing a service rather than gaining unauthorized access. The document outlines different types of DoS attacks like Smurf, SYN flood, and ping of death attacks. It also discusses tools used to carry out DoS and DDoS attacks such as Jolt2, Bubonic, and Blast2.0. Finally, it covers concepts like botnets and how they can enable large-scale DDoS attacks.
The document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It defines DoS and DDoS attacks, describes different types of DoS attacks like SYN flooding and Smurf attacks. It also explains how botnets and tools are used to launch DDoS attacks, and discusses some common DDoS countermeasures like detection, mitigation and traceback.
The document discusses various types of malware attacks including DDoS attacks, botnets, and mitigations. It provides definitions and examples of different malware types such as viruses, worms, Trojan horses, rootkits, logic bombs, and ransomware. It also discusses how botnets are used to launch DDoS attacks and describes common DDoS attack countermeasures such as preventing initial hacks, using firewalls, and changing targeted IP addresses.
This document discusses denial of service (DoS) attacks. It defines DoS as an attack meant to make a machine or network unavailable to its intended users. Several common DoS attack methods are described, including ICMP floods, teardrop attacks, and reflected/spoofed attacks. The document also provides information on tools used for DoS attacks and discusses how to identify an attack, what to do in response, and how to avoid being part of the problem.
Unleash the Hammer on Denial-of-Service: Conquer DDos Attacks!PriyadharshiniHemaku
Unleash the Hammer on Denial-of-Service: Conquer DDos Attacks!
This presentation cracks the code on devastating DDoS attacks, equipping you with insights and strategies to shield your systems and emerge victorious. Learn the devious tricks attackers use, explore robust defense mechanisms, and discover how to stay ahead of the curve in the ever-evolving cyber-warfare landscape. Prepare to turn the tables on malicious actors and ensure your operations run smoothly, even under siege!
Seven Ways To Be a Healthy Programmer!.pdfAhmed Salama
This document outlines 7 common health problems that programmers face from extensive computer use and provides suggestions for preventing each one. The problems discussed are eye strain, neck and back pain, wrist problems, lack of exercise and sleep, and mental health issues. Suggested preventions include taking regular breaks, stretching, using an ergonomic workstation, getting sufficient sleep, drinking water instead of caffeine, and practicing relaxation techniques.
10 Code Anti-Patterns to Avoid in Software Development.pdfAhmed Salama
The document discusses 10 code anti-patterns that developers should avoid in software development. These anti-patterns include: 1) The Golden Hammer where the same solution is used for different problems, 2) Spaghetti Code which is messy and unorganized, 3) Reinventing the Wheel by creating custom solutions instead of using existing libraries, 4) Dependency Hell which occurs when too many third-party libraries are imported, 5) God Classes that have too many responsibilities, 6) Hard Coding values instead of externalizing them, 7) Boat Anchor code that is written but not needed, 8) Lava Flow legacy code that is risky to change, 9) Copy-Paste Programming without reviewing code, and 10) Cargo Cult Programming
Ahmed Salama's document provides an introduction to web development, covering the history of the internet, the evolution to Web 2.0, and the current state of web development including client-side coding (frontend) versus server-side coding (backend). The document also outlines careers in web development such as front-end engineer, backend engineer, UI/UX designer, system administration, SEO and SEM, and technical support.
- Django is a free open source web framework written in Python that allows for rapid development of secure and maintainable websites.
- It follows the MVT (Model View Template) architectural pattern with Models representing data, Views handling business logic, and Templates for presentation.
- To create a Django project, you install Django, start a project with django-admin, add apps, define models, views, URLs, templates, and test. Django provides generated starter code and admin interface.
- An example Todo app was demonstrated with a Task model having fields like name, description, owner, responsibilities, and completion status.
Python is a multi-paradigm programming language created in 1989 by Guido van Rossum. It is based on ABC and Modula-3 and was named after Monty Python. Python has a simple syntax and dynamic typing and memory management. It can be used for web development, data science, scientific computing, and more. The core philosophy is summarized in the Zen of Python document. Python code is written, tested, and executed using integrated development environments like PyCharm or directly from the command line.
This document discusses distributed database systems. It begins by explaining that as databases get larger, it becomes difficult to store the entire database in a single location due to storage capacity and performance issues. It then lists some common reasons for using a distributed database, such as having data stored close to where it is used and allowing access from multiple branches.
It defines a distributed database system as a single logical database that is physically spread across multiple connected computer locations. A distributed database management system (DDBMS) manages the distributed database and makes the distribution transparent to users. Finally, it briefly describes some common types of distributed database systems, such as homogeneous systems with the same DBMS at each node, and heterogeneous systems with different DBMSs
Introduction to Computer Science DepartmentAhmed Salama
This document provides an overview of computer science. It discusses the fields of mathematics and computer science, including mathematics, statistics, and computer science. It defines a computer and describes what computers can do today and may do in the future, such as diagnose diseases and control robots. The study of computer science has roots in both mathematics and engineering. Reasons to study computer science include that computing is involved in everything, it offers opportunities for creativity and innovation, and leads to lucrative careers. Common fields in computer science are listed. The document also briefly discusses the software engineering and multimedia department.
“An Outlook of the Ongoing and Future Relationship between Blockchain Technologies and Process-aware Information Systems.” Invited talk at the joint workshop on Blockchain for Information Systems (BC4IS) and Blockchain for Trusted Data Sharing (B4TDS), co-located with with the 36th International Conference on Advanced Information Systems Engineering (CAiSE), 3 June 2024, Limassol, Cyprus.
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfMalak Abu Hammad
Discover how MongoDB Atlas and vector search technology can revolutionize your application's search capabilities. This comprehensive presentation covers:
* What is Vector Search?
* Importance and benefits of vector search
* Practical use cases across various industries
* Step-by-step implementation guide
* Live demos with code snippets
* Enhancing LLM capabilities with vector search
* Best practices and optimization strategies
Perfect for developers, AI enthusiasts, and tech leaders. Learn how to leverage MongoDB Atlas to deliver highly relevant, context-aware search results, transforming your data retrieval process. Stay ahead in tech innovation and maximize the potential of your applications.
#MongoDB #VectorSearch #AI #SemanticSearch #TechInnovation #DataScience #LLM #MachineLearning #SearchTechnology
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
GraphRAG for Life Science to increase LLM accuracyTomaz Bratanic
GraphRAG for life science domain, where you retriever information from biomedical knowledge graphs using LLMs to increase the accuracy and performance of generated answers
Programming Foundation Models with DSPy - Meetup SlidesZilliz
Prompting language models is hard, while programming language models is easy. In this talk, I will discuss the state-of-the-art framework DSPy for programming foundation models with its powerful optimizers and runtime constraint system.
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Unlocking Productivity: Leveraging the Potential of Copilot in Microsoft 365, a presentation by Christoforos Vlachos, Senior Solutions Manager – Modern Workplace, Uni Systems
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-und-domino-lizenzkostenreduzierung-in-der-welt-von-dlau/
DLAU und die Lizenzen nach dem CCB- und CCX-Modell sind für viele in der HCL-Community seit letztem Jahr ein heißes Thema. Als Notes- oder Domino-Kunde haben Sie vielleicht mit unerwartet hohen Benutzerzahlen und Lizenzgebühren zu kämpfen. Sie fragen sich vielleicht, wie diese neue Art der Lizenzierung funktioniert und welchen Nutzen sie Ihnen bringt. Vor allem wollen Sie sicherlich Ihr Budget einhalten und Kosten sparen, wo immer möglich. Das verstehen wir und wir möchten Ihnen dabei helfen!
Wir erklären Ihnen, wie Sie häufige Konfigurationsprobleme lösen können, die dazu führen können, dass mehr Benutzer gezählt werden als nötig, und wie Sie überflüssige oder ungenutzte Konten identifizieren und entfernen können, um Geld zu sparen. Es gibt auch einige Ansätze, die zu unnötigen Ausgaben führen können, z. B. wenn ein Personendokument anstelle eines Mail-Ins für geteilte Mailboxen verwendet wird. Wir zeigen Ihnen solche Fälle und deren Lösungen. Und natürlich erklären wir Ihnen das neue Lizenzmodell.
Nehmen Sie an diesem Webinar teil, bei dem HCL-Ambassador Marc Thomas und Gastredner Franz Walder Ihnen diese neue Welt näherbringen. Es vermittelt Ihnen die Tools und das Know-how, um den Überblick zu bewahren. Sie werden in der Lage sein, Ihre Kosten durch eine optimierte Domino-Konfiguration zu reduzieren und auch in Zukunft gering zu halten.
Diese Themen werden behandelt
- Reduzierung der Lizenzkosten durch Auffinden und Beheben von Fehlkonfigurationen und überflüssigen Konten
- Wie funktionieren CCB- und CCX-Lizenzen wirklich?
- Verstehen des DLAU-Tools und wie man es am besten nutzt
- Tipps für häufige Problembereiche, wie z. B. Team-Postfächer, Funktions-/Testbenutzer usw.
- Praxisbeispiele und Best Practices zum sofortigen Umsetzen
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
UiPath Test Automation using UiPath Test Suite series, part 6DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
UiPath Test Automation with generative AI and Open AI webinar offers an in-depth exploration of leveraging cutting-edge technologies for test automation within the UiPath platform. Attendees will delve into the integration of generative AI, a test automation solution, with Open AI advanced natural language processing capabilities.
Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
What will you get from this session?
1. Insights into integrating generative AI.
2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
4. Exploration of real-world use cases illustrating the benefits of AI-driven test automation for UiPath
Topics covered:
What is generative AI
Test Automation with generative AI and Open AI.
UiPath integration with generative AI
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
3. 3
• A DoS attack: preventing legal users, authorized access to a
system resource . The attacker uses specialized software to send
a flood of data packets to the target Device .
• DDoS ( distributed DoS attacks)
the attacker gains illegal administrative access to as many computers on the
Internet as possible and uses the multiple computers to send a flood of data
packets to the target Device
DoS = when a single host attacks
DDoS = when multiple hosts attack simultaneously
WHAT IS “DOS ATTACK”
6. Aim OF “DOS ATTACKS”
Purpose is to shut down a site, not penetrate it. may be
vandalism(including terrorism)
• Modification of internal data, change of programs
overloading the victim's resources
7. HISTORY
Morris Worm (November 2, 1988)
• First DDoS attack to cripple large amounts of network
infrastructure
• Self-replicating, self-propagating.
• Exploited software commonality (monoculture)
8. HISTORY
Morris Worm effect
• Infected systems became “catatonic “
• Took roughly three days to come under control
• Ultimately infected 10% of Internet computers (6,000) and
cost $ millions to clean up.
• Morris convicted under computer fraud and abuse act, three
years probation, fine of $10,000, he is now prof. At MIT
9. ESTONIAN CYBERWAR, 2007
• Weeks of cyber attacks followed, targeting government and banks,
ministries, newspapers and broadcasters Web sites of Estonia.
•
• 128 unique DDoS attacks
• Used hundreds or thousands of "zombie" computers and pelted Estonian
Web sites with thousands of requests a second
10. ESTONIAN CYBERWAR, 2007
• The attack heavily affected infrastructures of
all network:
– Routers damaged.
– Routing tables changed.
– DNS servers overloaded.
– Email servers mainframes failure, and etc.
11. In Feb 2000, series of massive DoS attacks incapacitated several high-
visibility Internet e-commerce sites, including Yahoo, Ebay and E*trade
In Jan 2001, Microsoft’s name sever infrastructure was disabled
>>98% of users could not get to any Microsoft’s servers
In Oct 2002, all Domain Name System servers were attacked
Attack lasted only an hour
9 of the 13 servers were seriously affected
In Aug 2009, the attack on Twitter and Facebook
HISTORY
12. Why should we care?
Internet is now a critical resource whose disruption has financial
implications, or even dire consequences on human safety
Cybercrime and cyberwarfare might use of DoS or DDoS as a potential
weapon to disrupt or degrade critical infrastructure
DDoS attacks are a major threat to the stability of the Internet
13. Pa
ge
The DoS Attack Surface
Any part of your network or
services that is vulnerable to
an attack
– Network Interfaces
– Infrastructure
– Firewall/IPS
– Servers
– Protocols
– Applications
– Databases
Attackers will find the
weakness
14. Distributed Denial-of-service
Attacker uses multiple PCs for DoS by:
Utilizing vulnerabilities to gain access to these systems
Installing malicious backdoor programs , thereby making zombies
Creating botnets: large collection of zombies under the control of
attacker
Generally, a control hierarchy is used to create botnets
Handlers: The initial layer of zombies that are directly controlled by the
attacker
Agent systems: Subordinate zombies that are controlled by handlers
Attacker sends a single command to handler, which then automatically
forwards it to all agents under its control
Example: Tribe Flood Network (TFN), TFN2K
15. 15
How They Work ?
Victim
Daemon
Daemon
Daemon
Daemon
Daemon
Master
Real Attacker
16. 16
How They Talk ?
Trinoo tool: attacker uses TCP; masters and daemons
use UDP; password authentication.
TFN ”Tribe Flood Network" tool: attacker uses shell to
invoke master; masters and daemons use ICMP
ECHOREPLY.
Stacheldraht tool: attacker uses encrypted TCP
connection to master; masters and daemons use TCP
and ICMP ECHO REPLY; rcp used for auto-update.
17. Approaches to DOS ATTACKS
Flooding attack
Work by sending a vast number of messages whose processing consumes
some key resource at the target
The strength lies in the volume, rather than the content
Implications :
Make the traffic look legitimate
Flow of traffic is large enough to consume victim’s resources
Send with high packet rate
19. Internet designed for minimal-processing and best-effort forwarding
any packet
Make shrewd use of flaws in the Internet design and systems
Vulnerability attack
Vulnerability : a bug in implementation or a bug in a default configuration
of a service
Malicious messages (exploits) : unexpected input that utilize the
vulnerability are sent
Consequences :
The system slows down or crashes or freezes or reboots
Target application goes into infinite loop
Consumes a vast amount of memory
Ex : Ping of death, teardrop attacks, etc.
Approaches to DOS ATTACKS
20. HOW TO DEFEND
• Firewalls - can effectively prevent users from launching simple
flooding type attacks from machines behind the firewall.
• Switches - Some switches provide automatic and/or system-
wide rate limiting, traffic shaping, delayed binding to detect
and remediate denial of service attacks
• Routers - If you add rules to take flow statistics out of the
router during the DoS attacks, they further slow down and
complicate the matter
• DDS based defense
• Clean pipes
Distributed Denial of Service Attacks could be Detected
by Monitoring the Source IP.
21. Airmon-ng start wlan0
Airodump-ng wlan0mon >> get mac Add. And target
channel
Iwconfig wlan0mon channel # >> edit your channel to
the target channel
Aireplay -0 500 -a MAC ADD. wlan0mon
-0> send deauthentication messages
500 > # of packets to send
-a > option [mac address the the interface ]
HOW TO DO THAT