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CITA 352

CITA 352. Chapter 5 Port Scanning. Introduction to Port Scanning. Port Scanning Finds which services are offered by a host Identifies vulnerabilities Open services can be used on attacks Identify vulnerable port and launch exploit Scans all ports when testing Not just well-known ports.

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CITA 352

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  1. CITA 352 Chapter 5 Port Scanning

  2. Introduction to Port Scanning • Port Scanning • Finds which services are offered by a host • Identifies vulnerabilities • Open services can be used on attacks • Identify vulnerable port and launch exploit • Scans all ports when testing • Not just well-known ports

  3. Figure 5-1 The AW Security Port Scanner interface

  4. Introduction to Port Scanning (cont’d.) • Port scanning programs report: • Open ports • Closed ports • Filtered ports • Best-guess running OS

  5. Types of Port Scans • SYN scan • Stealthy scan • Connect scan • Completes three-way handshake • NULL scan • Packet flags are turned off • XMAS scan • FIN, PSH and URG flags are set

  6. Types of Port Scans (cont’d.) • ACK scan • Used to get past firewall • FIN scan • Closed port responds with an RST packet • UDP scan • Closed port responds with ICMP “Port Unreachable” message

  7. Using Port-Scanning Tools • Port-scanning tools • Hundreds available • Not all are accurate • Be familiar with a variety • Practice often • Some tools include: • Nmap • Unicornscan • Nessus and OpenVAS

  8. Nmap • Originally written for Phrack magazine • One of the most popular tools • New features frequently added • GUI front end • Zenmap • Standard tool for security professionals • Command: nmap 193.145.85.201 • Scans every port on computer with this IP address

  9. Figure 5-2 The Nmap help screen

  10. Unicornscan • Developed to assist with large network tests • Ideal for large-scale endeavors • Scans 65,535 ports in three to seven seconds • Handles port scanning using: • TCP • ICMP • IP • Optimizes UDP scanning

  11. Nessus and OpenVAS • Nessus • First released in 1998 • No longer under GPL license • Still available for download • OpenVAS • Open-source fork of Nessus • Performs complex queries while client interfaces with server • Capable of updating security check plug-ins • Security test programs (scripts)

  12. Figure 5-3 OpenVAS with a safe checks warning

  13. Figure 5-4 OpenVAS discovers a vulnerability

  14. Conducting Ping Sweeps • Ping sweeps • Identify which IP addresses belong to active hosts • Ping a range of IP addresses • Problems • Shut down computers cannot respond • Networks may be configured to block ICMP Echo Requests • Firewalls may filter out ICMP traffic

  15. FPing • Ping multiple IP addresses simultaneously • Accepts a range of IP addresses • Entered at a command prompt • File containing multiple IP addresses • Input file • Usually created with shell-scripting language

  16. Figure 5-5 Fping parameters

  17. Figure 5-6 Results of an Fping command

  18. Hping • Used to: • Perform ping sweeps • Bypass filtering devices • Allows users to inject modified IP packets • Powerful tool • All security testers must be familiar with tool • Supports many parameters

  19. Figure 5-7 Hping help, page 1

  20. Figure 5-8 Hping help, page 2

  21. Figure 5-9 Hping help, page 3

  22. Crafting IP Packets • Packet components • Source IP address • Destination IP address • Flags • Helps obtain information about a service • Tools: • Hping • Fping

  23. Understanding Scripting • Modify tools to better suit your needs • Customized scripts • Automates tasks • Time saving • Requires basic programming skills

  24. Scripting Basics • Similar to DOS batch programming • Script or batch file • Text file • Contains multiple commands • Repetitive commands • Good candidate for scripting • Practice is the key

  25. Table 5-1 Summary of vi commands

  26. Figure 5-10 A shell script

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