This document summarizes different types of network scans that can be performed using Nmap, including TCP connect scans, SYN scans, FIN scans, Xmas scans, Null scans, and least traffic scans. It also discusses why vulnerability scanning is important and compares the features of the free Nessus Home Feed versus the paid Professional Feed for vulnerability scanning. The Professional Feed provides more frequent plugin updates, policy compliance checks, unlimited PCI audits, operating system audits, and technical support compared to the free Home Feed.

1. Network Security 2 assignment Presentation By Sarah deoriUtkarshVermaVandan Joshi Vijay ShuklaRowinChineah

2. TCP connect scan

3. TCP connect() ScanningTheconnect() system call provided by your operating system is used to open a connection to every interesting port on the machine. If the port is listening, connect() will succeed, otherwise the port isn't reachable.AdvantageDon’t need Special PrivilegesSpeedDisadvantageEasily detectable and filterable

4. SYN scan

5. Advantages of syn scanThe TCP SYN scan never actually creates a TCP session, so isn't logged by the destination host's applicationsSince an application session is never opened, the SYN scan is also less stressful to the application service.Disadvantages of syn scanThe TCP SYN scan requires that nmap have privileged access to the system. Without privileged access, nmap can't create the raw packets necessary for this half-open connection process.Fin scan

6. Xmas scan

7. Null scan

8. Least traffic scanSteath Scanning - The FIN Scan (-sF), Xmas Tree Scan (-sX), and Null Scan (-sN)Requires Privileged Access: YESIdentifies TCP Ports: YESIdentifies UDP Ports: NOThese are called "stealth" scans because they send a single frame to a TCP port without any TCP handshaking or additional packet transfersNMAP response for These SCANClosedOpen|FilteredThe open|filtered result is combined because firewalls often drop these frames without a response

9. Undetectable scanThe XMAS scan determines which ports are open by sending packets with invalid flag settings to a target device. It is considered a stealth scan because it may be able to bypass some firewalls and IDSes more easily than the SYN scans. The Nmap XMAS scan sends packets with the Finish (FIN), Push (PSH), and Urgent (URG) flags set.Because this flag combination is invalid and should never occur in normal traffic, there is no established convention for dealing with these types of packets. Different TCP stacks will respond in different ways. Typically, closed ports will respond with a RST/ACK, and open ports will drop the packet and not respond. However, some TCP stacks will respond with RST packets from all ports, even open ports, and some systems will not respond to any packets. Personal firewalls and packet filters will also alter responses to this scan

10. XMAS Scan

11. why vulnerability scanAlthough network scanning identifies active hosts, ports, services, and applications, vulnerability scanning goes one step further to identify weaknesses and vulnerabilities on a system that may be exploited by an attacker

12. Is Nessus ideal open-source vulnerability scannerIts goal to detectVulnerabilities that allow a remote cracker to control or access sensitive data on a system.MisconfigurationDefault passwords, a few common passwords, and blank/absent passwords on some system accounts. Nessus can also call Hydra (an external tool) to launch a dictionary attack.

13. Nessus Operation In typical operation, Nessus begins by doing a port scan with one of its four internal port scanners to determine which ports are open on the target and then tries various exploits on the open ports. The vulnerability tests, available as subscriptions, are written in NASL (Nessus Attack Scripting Language), a scripting language optimized for custom network interaction.

14. Difference between nessus professional and home feed Commercial organizations which use the Nessus vulnerability scanner must purchase a Professional Feed subscription to scan their network, obtain support, updates to their database of vulnerability checks and compliance auditingA 'Home Feed' is available for free to home users, but can not be used professionally.There are more features of Proffessional Feed than home feed

15. Features of Professional feed NessusThe newest Nessusplugins as soon as they are released Policy Compliance Checks - to make sure every host on your network complies with your local security policy. Perform an unlimited amount of complete PCI-DSS audits Conduct operating system, application and SQL database configuration audits against CERT, CIS, DISA STIGs, GLBA, HIPAA, NIST SCAP FDCC, NSA and PCI standards. Conduct content audits such as adult content, personally identifiable information (credit cards, SSN, etc.) corporate spreadsheets, and much more. Perform web application audits of custom and embedded applications to test for cross site scripting, SQL injection and much more. SCADA checks to detect and audit SCADA devices Virtual Appliance - access to a download of the Tenable Appliance which includes Nessus 4 and works with VMware ESX, Server, Workstation and Fusion. Access to operational and technical assistance from Tenable's experienced support staff with regards to the deployment and use of their scanners, as well as the writing of audit policies for the compliance checks or content checks.