Network Security Module 1 – Overview of Network Security
1.1 Introduction to Network Security
1.2 Introduction to Vulnerabilities, Threats, and Attacks
1.3 Attack Examples
1.4 Vulnerability Analysis
Module 1 – Overview of Network Security 1.1 Introduction to Network Security
Network security is the process by which digital information assets are protected.
The goals of security are to protect confidentiality, maintain integrity, and assure availability . With this in mind, it is imperative that all networks be protected from threats and vulnerabilities in order for a business to achieve its fullest potential.
Typically, these threats are persistent due to vulnerabilities, which can arise from misconfigured hardware or software, poor network design, inherent technology weaknesses, or end-user carelessness .
The Closed Network
The Network Today
Identifying Potential Risks
A risk analysis should identify the risks to the network, network resources, and data. The intent of a risk analysis is to identify the components of the network, evaluate the importance of each component, and then apply an appropriate level of security. This helps to maintain a workable balance between security and required network access.
Network Security Models
Open Security Model
Open Security Model
Restricted Security Model
Closed Security Model
Closed Security Model
Technology that affect Security
Trends that Affect Security
Increase of network attacks
Increased sophistication of attacks
Increased dependence on the network
Lack of trained personnel
Lack of awareness
Lack of security policies
Organization of information security
Human resources security
Physical and environmental security
Communications and operations management
Information systems acquisition, development and maintenance
Information security incident management
Business continuity management
Module 1 – Overview of Network Security 1.2 Introduction to Vulnerabilities, Threats, and Attacks
Vulnerability is a weakness which is inherent in every network and device. This includes routers, switches, desktops, servers, and even security devices themselves.
Threats are the people eager, willing, and qualified to take advantage of each security weakness, and they continually search for new exploits and weaknesses.
Finally, the threats use a variety of tools, scripts, and programs to launch attacks against networks and network devices.
Technology : Computer and network technologies have intrinsic security weaknesses. These include TCP/IP protocol, operating system, and network equipment weaknesses
Configuration : Network administrators or network engineers need to learn what the configuration weaknesses are and correctly configure their computing and network devices to compensate.
Policy : The network may pose security risks to the network if users do not follow the security policy.
Security Policy Weaknesses
Threat Capabilities — More Dangerous and Easier to Use
Variety of Threats
The four primary attack categories
Module 1 – Overview of Network Security 1.3 Attack Examples
There are four general categories of security threats to the network:
Internet External exploitation Internal exploitation Dial-in exploitation Compromised host
Four Classes of Network Attacks
Denial of service attacks
Worms, viruses, and Trojan horses
Specific Attack Types
All of the following can be used to compromise your system:
DoS or DDoS
Application layer attacks
Network reconnaissance refers to the overall act of learning information about a target network by using publicly available information and applications.
Reconnaissance Attack Example
Sample IP address query
Sample domain name query
Reconnaissance Attack Mitigation
Network reconnaissance cannot be prevented entirely.
IDSs at the network and host levels can usually notify an administrator when a reconnaissance gathering attack (for example, ping sweeps and port scans) is under way.
A packet sniffer is a software application that uses a network adapter card in promiscuous mode to capture all network packets. The following are the packet sniffer features:
Packet sniffers exploit information passed in clear text. Protocols that pass information in the clear include the following:
Packet sniffers must be on the same collision domain.
Host A Host B Router A Router B
Packet Sniffer Mitigation
The following techniques and tools can be used to mitigate sniffers:
Authentication —Using strong authentication, such as one-time passwords, is a first option for defense against packet sniffers.
Switched infrastructure —Deploy a switched infrastructure to counter the use of packet sniffers in your environment.
Antisniffer tools —Use these tools to employ software and hardware designed to detect the use of sniffers on a network.
Cryptography —The most effective method for countering packet sniffers does not prevent or detect packet sniffers, but rather renders them irrelevant.
Host A Host B Router A Router B
Port Scan Example
Access attacks exploit known vulnerabilities in authentication services, FTP services, and Web services to gain entry to Web accounts, confidential databases, and other sensitive information . Access attacks can consist of the following:
Hackers can implement password attacks using several different methods:
Trojan horse programs
Password Attacks Mitigation
The following are mitigation techniques:
Do not allow users to use the same password on multiple systems.
Disable accounts after a certain number of unsuccessful login attempts.
Do not use plain text passwords. OTP or a cryptographic password is recommended.
Use “strong” passwords. Strong passwords are at least eight characters long and contain uppercase letters, lowercase letters, numbers, and special characters.
A man-in-the-middle attack requires that the hacker have access to network packets that come across a network.
A man-in-the-middle attack is implemented using the following:
Network packet sniffers
Routing and transport protocols
Possible man-in-the-middle attack uses include the following:
Theft of information
Hijacking of an ongoing session
Corruption of transmitted data
Introduction of new information into network sessions
Host A Host B Router A Router B Data in clear text
Man-in-the-middle attacks can be effectively mitigated only through the use of cryptography (encryption).
Host A Host B Router A ISP Router B A man-in-the-middle attack can only see cipher text IPSec tunnel
They prevent authorized people from using a service by using up system resources. The following are examples of common DoS threats:
Ping of death
SYN flood attack
Packet fragmentation and reassembly
DDoS attacks are designed to saturate network links with spurious data. This data can overwhelm an Internet link, causing legitimate traffic to be dropped . DDoS uses attack methods similar to standard DoS attacks but operates on a much larger scale. Typically hundreds or thousands of attack points attempt to overwhelm a target. Examples of DDoS attacks include the following:
Tribe Flood Network (TFN)
DDoS Attack Example
DoS Attack Mitigation
The threat of DoS attacks can be reduced through the following three methods:
Antispoof features —Proper configuration of antispoof features on your routers and firewalls
Anti-DoS features —Proper configuration of anti-DoS features on routers and firewalls
Traffic rate limiting —Implement traffic rate limiting with the networks ISP
IP spoofing occurs when a hacker inside or outside a network impersonates the conversations of a trusted computer.
Two general techniques are used during IP spoofing:
A hacker uses an IP address that is within the range of trusted IP addresses.
A hacker uses an authorized external IP address that is trusted.
Uses for IP spoofing include the following:
IP spoofing is usually limited to the injection of malicious data or commands into an existing stream of data.
A hacker changes the routing tables to point to the spoofed IP address, then the hacker can receive all the network packets that are addressed to the spoofed address and reply just as any trusted user can.
IP Spoofing Mitigation
The threat of IP spoofing can be reduced, but not eliminated, through the following measures:
Access control —The most common method for preventing IP spoofing is to properly configure access control.
RFC 2827 filtering —You can prevent users of your network from spoofing other networks (and be a good Internet citizen at the same time) by preventing any outbound traffic on your network that does not have a source address in your organization's own IP range.
Additional authentication that does not use IP-based authentication—Examples of this include the following:
Strong, two-factor, one-time passwords
Application Layer Attacks
Application layer attacks have the following characteristics:
Exploit well known weaknesses, such as protocols , that are intrinsic to an application or system (for example, sendmail, HTTP, and FTP)
Often use ports that are allowed through a firewall (for example, TCP port 80 used in an attack against a web server behind a firewall)
Can never be completely eliminated, because new vulnerabilities are always being discovered
Application Layer Attacks Mitigation
Some measures you can take to reduce your risks are as follows:
Read operating system and network log files , or have them analyzed by log analysis applications.
Subscribe to mailing lists that publicize vulnerabilities.
Keep your operating system and applications current with the latest patches .
IDSs can scan for known attacks, monitor and log attacks , and in some cases, prevent attacks.
Virus and Trojan Horses
Viruses refer to malicious software that are attached to another program to execute a particular unwanted function on a user’s workstation. End-user workstations are the primary targets.
A Trojan horse is different only in that the entire application was written to look like something else, when in fact it is an attack tool. A Trojan horse is mitigated by antivirus software at the user level and possibly the network level.
Worm attack mitigation
Vulnerabilities Exist at all OSI Layers
Module 1 – Overview of Network Security 1.4 Vulnerability Analysis
Network Security Policy
The network security policy is a broad, end-to-end document designed to be clearly applicable to an organization's operations. The policy is used to aid in network design, convey security principles, and facilitate network deployments.
The network security policy outlines rules for network access, determines how policies are enforced, and describes the basic architecture of the organization's network security environment.
The policy should identify the assets that require protection. This will help the designer provide the correct level of protection for sensitive computing resources, and identify the flow of sensitive data in the network.
The policy should identify possible attackers . This will give the designer insight into the level of trust assigned to internal and external users, ideally identified by more specific categories such as business partners, customers of an organization, outsourcing IT partners.
Network security Policies
SDN Topology Cisco NAC Appliance & Cisco Security Agent Cisco IOS Firewall, VPN Software, access control & Filtering Cisco IOS Firewall, VPN Software, access control & Filtering Cisco IOS Firewall, Cisco adaptive security appliance Traffic inspection and threat mitigation Cisco security monitoring, analisys, and response system Cisco security Manager provides policy-based management
To secure the management and forwarding planes of the router, use the auto secure command in privileged EXEC mode.
auto secure [management | forwarding] [no-interact]
management (Optional) Only the management plane will be secured.
forwarding (Optional) Only the forwarding plane will be secured.
no-interact (Optional) The user will not be prompted for any interactive configurations. If this keyword is not enabled, the command will show the user the noninteractive configuration and the interactive configurations thereafter.
NSA Router Security Guide
CIS RAT Report
Network Mapper (Nmap) – Nmap is a very popular free tool used for security scanning and auditing. It can rapidly perform a port scan of a single host or a range of hosts. Nmap was originally written to be run on UNIX systems, and it is now available for use on Microsoft Windows platforms .
Nessus – Nessus is a vulnerability scanner that is available for UNIX and Microsoft Windows platforms. New vulnerability testing capabilities can be added to Nessus through the installation of modular plugins. Nessus includes a built in port scanner, or it can be used along with Nmap. Once the Nessus scan is finished, a report is created. This report displays the results of the scan and provides steps that can be taken to mitigate vulnerabilities.
Microsoft Baseline Security Analyzer
The Microsoft Baseline Security Analyzer (MBSA) can be used to scan hosts running Windows 2000, Windows Vista, Windows XP, and Windows Server 2003 & 2008 operating systems to determine potential security risks.
MBSA scans for common system misconfigurations and missing security updates. MBSA includes both a graphical and command line interface that can perform local or remote scans.
After a system scan, the MBSA provides a report outlining potential vulnerabilities and the steps required to correct them.