Karlstad University Introduction to Vulnerability Assessment Labs Ge Zhang Dvg-C03

Karlstad University Schedule 3 Attacking methods –Password cracking –ARP spoofing & sniffing –Port Scanning 1 Defense methods –Firewall configuration 2 Vulnerability assessment tool –Nessus –Bastille

Karlstad University Environment 3 VM images ( c:\vmware\valab-ht11 )

Karlstad University Password Cracking Authentication: –Something you know –Something you have –Something you are Password need to be transferred Password need to be stored

Karlstad University 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

Karlstad University 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

Karlstad University 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 Have a look on –/usr/share/doc/john /EXAMPLES Then create your own account and password, run “john” again to see the result useradd [your account] passwd [your account]

Karlstad University 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

Karlstad University Wireshark

Karlstad University Wireshark

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

Karlstad University ARP (Address Resolution Protocol) MAC address (layer 2) –Global unique –Unchangeable IP address (layer 3) –Network unique –Changeable

Karlstad University ARP spoofing (cache poisoning) on switch

Karlstad University Preparation ipconfig /all Let me know the last number of your ip address and mac address ping [IP address] –t

Karlstad University Cain

Karlstad University Cain

Karlstad University Cain

Karlstad University 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 …

Karlstad University 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)

Karlstad University Nmap

Karlstad University Nmap Zenmap: graphical interface

Karlstad University 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.

Karlstad University 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.

Karlstad University 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.

Karlstad University 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

Karlstad University Nessus Client/server architecture –Server: perform checking –Client: Front-end Can test unlimited amount of hosts in each scan

Karlstad University Nessus

Karlstad University Nessus

Karlstad University 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

Karlstad University Bastille Assessment mode: bastille -a

Karlstad University Bastille Configuration mode: bastille -x