Covering tracks is a crucial phase in penetration testing, especially in scenarios where the pentester needs to ensure that their activities remain undetected. This phase involves removing or altering evidence of the pentester's presence and actions on the target system. While this practice is essential for ethical hackers to understand, it is also a technique used by malicious actors to avoid detection.

1. Log Files:

   • Log files record various activities on a system, including user logins, file access, and system errors.
   • Common log files include system logs, application logs, and security logs.

2. Log Manipulation:

   • Deleting or altering log entries to remove traces of the pentester's activities.
   • Tools and commands can be used to edit or clear logs.

3. File and Process Hiding:

   • Techniques to hide files and processes from system administrators and security tools.
   • Rootkits and other stealth tools can be used for this purpose.

4. Network Traffic Obfuscation:

   • Techniques to disguise or encrypt network traffic to avoid detection by network monitoring tools.
   • Use of VPNs, proxies, and encrypted communication channels.

5. Clearing Command History:

   • Removing or altering the command history to hide executed commands.
   • Commands like history -c in Linux can clear the command history.

Explanation:

• truncate -s 0 /var/log/syslog: This command sets the size of the syslog file to 0, effectively clearing its contents.
• truncate -s 0 /var/log/auth.log: Similarly, this command clears the authentication log file.
• history -c: This command clears the current user's bash command history.

Note: This example is for educational purposes only. Using rootkits can be illegal and unethical outside of a controlled and authorized environment.

Explanation:

• rkhunter: Rootkit Hunter is a tool that scans for rootkits, but some rootkits can be used to hide files and processes.
• --propupd: This option updates the file properties database, which can be manipulated by a rootkit to hide files.

Explanation:

• openvpn --config myvpnconfig.ovpn: This command starts an OpenVPN connection using the specified configuration file, encrypting the network traffic and making it harder to detect.

Task: Write a script to clear specific log entries related to a user login event in the /var/log/auth.log file.

Solution:

Explanation:

• USERNAME="targetuser": Define the username whose log entries need to be removed.
• cp /var/log/auth.log /var/log/auth.log.bak: Backup the original log file.
• grep -v "$USERNAME" /var/log/auth.log.bak > /var/log/auth.log: Use grep -v to filter out lines containing the username and write the result to the original log file.
• history -c: Clear the bash history to remove traces of the executed commands.

• Mistake: Forgetting to backup log files before modifying them.

  • Tip: Always create a backup of log files before making any changes to avoid accidental data loss.

• Mistake: Clearing all logs indiscriminately.

  • Tip: Target specific log entries to avoid raising suspicion by completely emptying log files.

• Mistake: Not considering the impact on system stability.

  • Tip: Ensure that the actions taken to cover tracks do not disrupt normal system operations.

Covering tracks is a critical skill for pentesters to understand, as it helps them simulate real-world attack scenarios where attackers attempt to remain undetected. By learning techniques such as log manipulation, file and process hiding, and network traffic obfuscation, pentesters can better understand the methods used by malicious actors and improve their defensive strategies. Always remember to practice these techniques ethically and within the bounds of the law.