DFSP # 426 - SSH Forensics: Log Analysis

Summary

In this episode of the Digital Forensics Survival Podcast, host Michael concludes a three-part series on SSH forensics, focusing on the importance of SSH log triage. He discusses different log types, including firewall and system logs, highlighting the nuances of interpreting SSH connection records. Michael emphasizes the necessity of understanding the context of logs to avoid inaccuracies in investigations, particularly in determining successful connections and cryptographic key exchanges. Listeners gain valuable insights into effective methodologies for conducting thorough forensic analyses of SSH activity, essential for incident responders and forensic analysts.

Takeaways

• 🔍 Understanding SSH logs is crucial for accurate digital forensics, especially when conducting a compromise assessment or forensic exam.
• 📝 SSH log triage typically begins with firewall logs, which can provide initial insights into SSH activity but should be interpreted cautiously.
• ⚠️ A successful connection in firewall logs only indicates that the traffic was allowed through; it does not confirm a successful SSH session or terminal access.
• 📊 Key indicators in firewall logs include connection attempts, authentication methods, and session establishment, but care must be taken in their interpretation.
• 🔑 System logs, such as secure, auth, and sshd logs, contain detailed records of successful logins and cryptographic key exchanges essential for verification.
• 📂 Common log files to check include '/var/log/secure', '/var/log/auth.log', and '/var/log/sshd.log' for SSH-related events.
• ✅ Successful SSH authentication should be validated by a series of logged entries indicating the establishment of a connection and successful login.
• 🔎 Keywords for searching logs include 'sshd', 'accepted public key', and 'session opened', which can help identify relevant SSH records.
• 📈 It's important to look for patterns such as repeated failed login attempts, which could indicate unauthorized access attempts.
• 📚 Mastering SSH log analysis is a vital skill for incident responders and forensic analysts in enhancing security measures.

Q & A

What is the main topic of the podcast episode?

The main topic of the podcast episode is Linux log analysis, specifically focusing on SSH forensics and log triage.

What are the types of logs discussed in relation to SSH connections?

The types of logs discussed include firewall logs and system logs, which provide records of SSH connections.

Why should analysts be cautious when interpreting firewall logs for SSH connections?

Analysts should be cautious because firewall logs only indicate whether a connection was allowed or denied, not whether a successful SSH session was established.

What does a 'successful' connection in firewall logs actually signify?

A 'successful' connection in firewall logs signifies that the connection passed through the firewall but does not confirm a successful SSH session or terminal access.

What specific details can firewall logs provide regarding SSH connections?

Firewall logs can provide details such as source and destination IP addresses, port numbers, the outcome of connection attempts (success or failure), authentication information, and data transfer amounts.

What key log files should analysts check for SSH-related events on a Linux system?

Analysts should check the secure log, auth log, SSH daemon logs, system logs, and audit logs if enabled, all typically located in the /var/log directory.

What evidence indicates a successful SSH login according to the podcast?

Evidence of a successful SSH login includes records of connection establishment, successful authentication, session opening, and corresponding log entries confirming these actions.

What are some useful keywords for searching SSH logs?

Useful keywords include 'sshd', 'accepted public key', 'session opened', 'session terminated', and 'PTY allocation request', among others.

How can analysts validate suspicious SSH activity found in firewall logs?

Analysts can validate suspicious SSH activity by cross-referencing findings with system logs to confirm successful key exchanges and authenticated sessions.

What overarching skills are highlighted as essential for incident responders?

Being comfortable working with SSH artifacts and conducting effective triage for evidence surrounding malicious use of SSH are essential skills for incident responders.