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Introduction to Vulnerability Assessment Labs

This lab focuses on understanding various attacking and defense methods related to network security vulnerabilities. We will explore traffic sniffing with Wireshark, ARP spoofing, password cracking techniques, and port scanning with Nmap. Additionally, we will discuss defense strategies including firewall configurations and the use of vulnerability assessment tools such as Nessus and Bastille. The lab incorporates hands-on practice in a virtual environment with specific VM images, aiming to equip participants with the knowledge to secure networks effectively.

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Introduction to Vulnerability Assessment Labs

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  1. Introduction to Vulnerability Assessment Labs Ge Zhang ge.zhang@kau.se Dvg-C03

  2. Schedule • 4 Attacking methods • Traffic sniffing • ARP spoofing • Password cracking • Port Scanning • 1 Defense methods • Firewall configuration • 2 Vulnerability assessment tool • Nessus • Bastille • Summarizing Report on its learning (1-2 pages)

  3. Environment • 3 VM images (c:\VMware\valab-ht10\) • Windows, Fedora (angel), Fedora (devil)

  4. Sniffing • Hub: a hub simply receives incoming packets and broadcasts these packets out to all devices on the network • Adapt promiscuous mode: an adapter can receive all frames on the network, not just frames are addressed to that adapter

  5. Wireshark

  6. Wireshark

  7. Sniffing practice • Surfing with the browser on the host machine • Sniff the HTTP traffic using wireshark on the VM

  8. Hub v.s. switch • Hub: Layer 1 (physical) • Switch: Layer 2 (data-link)

  9. ARP (Address Resolution Protocol) • MAC address (layer 2) • Global unique • Unchangeable • IP address (layer 3) • Network unique • Changeable

  10. ARP spoofing (cache poisoning) on switch

  11. Preparation • ipconfig /all • Let me know the last number of your ip address and mac address • ping [hostname] –t

  12. Cain

  13. Cain

  14. Cain

  15. Password Cracking • Authentication: • Something you know • Something you have • Something you are • Password need to be transferred • Password need to be stored

  16. Brute Force • Attempts all possible combinations of letters and numbers • Possible Solution • Limit amount of unsuccessful logins • Change password often • The length should be at least 8 characters

  17. Dictionary • Type of Brute Force • Only tries possibilities that are likely to succeed • List are derived from dictionary • Possible Solutions • Mix and match numbers, letters, upper and lower case • Avoid passwords based on dictionary words, letter or number sequences, usernames, or biographical information

  18. John the ripper • Traditionally the account information is stored in the /etc/passwd file • The /etc/passwd file is world-readable • Shadow password system stores passwords in the file /etc/shadow which is not world-readable • unshadow /etc/passwd /etc/shadow > tmp • less tmp /*have a look*/ • john tmp • Then create your own account and password, run “john” again to see the result • useradd [your account] • passwd [your account]

  19. Port Scanning • Attackers wish to discover services they can break into. • Whether the service existing? • sending a packet to each port, once at a time. • Based on the type of response, an attacker knows if the port is used. • The used ports can be probed further for weakness. • Well-known: tcp 21, tcp 22, tcp 23, tcp 80 …

  20. Nmap • -sT (scanning by TCP connections) • -sS (SYN scanning) • -sU (UDP scanning) • -sV (Version detection) • -O (OS fingerprinting) • -T[0-5] (time interval) • -f (fragmenting)

  21. Nmap

  22. Nmap • Zenmap: graphical interface

  23. Firewall • A set of related programs that protects the resources of a private network or a host from external environment. • A mechanism for filtering network packets based on information contained within the IP header.

  24. IPtables 3 default chains • input Used to control packets entering the interface. (The packets will be ended in this machine) • output Used to control packets leaving the interface. (The packets are originated from this machine) • forward Used to control packets being masqueraded, or sent to remote hosts.

  25. IPtables • iptables command [match] [target] • Command: -A, -I, -D, -F, -L • Match: -p [protocol], -s [source IP], -d [destination IP], -i [interface], --sport [source port], --dport [destination port] • Target: -j [ACCEPT/DROP/LOG…] • Example: • iptables –I INPUT –p ICMP –j DROP • iptables –I INPUT –p ICMP –icmp-type 0 –j ACCEPT • Our task: restrict all inbound traffic, except SSH requests on port 22. However, any outgoing requests should not be affected.

  26. Nessus • Remote vulnerability scanner • Nessus will • Perform over 900 security checks • Accept new plugins to expand new checks • List security concerns and recommend actions to correct them

  27. Nessus • Client/server architecture • Server: perform checking • Client: Front-end • Can test unlimited amount of hosts in each scan

  28. Nessus

  29. Nessus

  30. Bastille • Operating System Hardening • Remove unnecessary processes • Setting file permissions • Patching and updating • Setting networking access controls • Generate your own hardening policy • Can be run manually to provide advice and information

  31. Bastille • Assessment mode: bastille -a

  32. Bastille • Configuration mode: bastille -x

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