A.P.E.X: Threat Hunting Through Structured Hypothesis Generation

 

In a laest report I worked on Hunters International ransomware, I provided several hypotheses you can implement in your environment. I want to reiterate the importance of integrating environmental context with threat actor profiling, a crucial aspect of threat hunting. I want to re-introduce the A.P.E.X. framework, which we used in our other threat reports, and delve a little deeper into its implementation with an example. A.P.E.X. hypothesis generation framework is a comprehensive methodology I developed internally for hypothesis generation. It is

Four-Element Structure: The A.P.E.X. framework integrates both perspectives through four key elements: Analyzing the environment, Profiling threats, Exploring anomalies, and examining X-factors (unexpected variations). This integration proved crucial in our investigation. The framework offers a structured, and adaptable methodology that aids threat hunters in generating hypotheses for both known and emerging trends.

• X-Factor Consideration: A.P.E.X. explicitly accounts for unexpected or unexpected threat techniques through its X-factor element. This approach hopes to help hunters account for emerging threats.
• Hypothesis Generation: A.P.E.X. offers a structured approach to creating both primary and focused hypotheses, providing more granularity and direction for threat hunters.
• Expected Observations: For every hypothesis, A.P.E.X. outlines detailed expected observations, categorized into standard (E) and unexpected (X) observations. This can also be translated into success criteria.
• Integration of Multiple Techniques: The framework takes various threat-hunting "techniques", including hypothesis-driven hunting, anomaly detection, and threat intelligence integration.

Theory to Practice:

A.P.E.X. can be used to generate the following hypothesis:

"Attackers are exploiting Oracle WebLogic debug ports for initial access."

A (Analyzing the environment): Oracle WebLogic servers were present in the environment, and debug ports were potentially exposed.

P (Profiling threats): Hunters International has shown a pattern of exploiting web server vulnerabilities.

E (Exploring anomalies): The unusual connections to port 8453 (WebLogic debug port) were noticed in the network logs.

X (X-factor): Attackers might use novel exploitation techniques or zero-day vulnerabilities.

Expected Observations:

E1: Connections to port 8453 from external IP addresses.

E2: Execution of Java processes with debug parameters.

E3: Creation of web shells or other backdoors post-exploitation.

X1: Unusual Java class loading or reflection activities indicating a new exploitation method.

X-factor consideration leads to unique insights:

We explicitly included the X-factor in the overall hypothesis generation process to account for novel or unexpected attacker behaviors based on patern-projections. This approach allows threat hunters to project and hunt emerging threats that may not fit already established patterns observed. In this case, it helped us discover an exploitation technique for Oracle WebLogic servers. Considering beyond known tactics, techniques, and procedures (TTPs), the X-factor enables a more forward-looking threat-hunting approach. While monitoring for expected observations (E1-E3), we also looked for X1 - unusual Java activities. This led to the finding of a previously unknown method of exploiting WebLogic.

• Attackers used a custom Java class to execute arbitrary code.
• We observed unusual Java class loading patterns that didn't match known exploit techniques for the group.

This approach generated specific, actionable observations and helped track the other activities in the attack lifecycle:

E1: Connections to port 8453 helped identify potential initial compromise, scoping, and timeline.

E2: Execution of Java processes with debug parameters revealed the attacker's method of maintaining access.

E3: The creation of the "Intel" folder and China Chopper web shell was detected allowed us to identify compromised systems quickly.

X1: Unusual Java class loading was observed, indicating a potential new exploit technique.

By following these detailed observations, I was able to track the attack progression from initial access through lateral movement and ultimately to the ransomware deployment, providing a comprehensive view of the Hunters International operation and enabling more effective intrusion analysis and hunting strategies.

Hope this helps. Happy Hunting!!