Add Queue APC injection signature

[kevross33]

Pikabot (also other malware like AgentTesla etc.)

[gemini-code-assist]

Summary of Changes

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This pull request introduces a new detection signature designed to identify Asynchronous Procedure Call (APC) injection attempts. This technique is frequently employed by various malware families, including Pikabot and AgentTesla, to execute malicious code within legitimate processes. The new signature enhances the system's ability to detect and flag such evasive behaviors by monitoring specific Windows API calls for suspicious cross-process activity.

Highlights

• New APC Injection Signature: A new signature, ApcInjection, has been added to detect Asynchronous Procedure Call (APC) injection, a technique used by malware for code execution and evasion.
• API Monitoring: The signature specifically monitors NtQueueApcThread and QueueUserAPC API calls to identify suspicious activity.
• Cross-Process Detection: It focuses on detecting cross-process APC injections where a non-null APC routine is queued to a thread in a different process, a common indicator of malicious intent.

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Changelog

• modules/signatures/windows/injection_thread.py
  • Added a new ApcInjection class to detect cross-process APC injection.

Activity

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[gemini-code-assist]

Code Review

This pull request adds a new signature to detect APC injection. The implementation is a good start, but has a significant logic flaw that could lead to false positives. I've provided a suggestion to fix the cross-process detection logic and make it more robust. I also included a minor style fix. After addressing these points, the signature should be much more reliable.

[gemini-code-assist]

The current logic for detecting cross-process APC injection is flawed and can lead to false positives.

1. targetpid can be None if the ProcessId argument is not available for the API call. In this case, the comparison pid != targetpid will evaluate to True, causing any APC call without a ProcessId to be flagged incorrectly.
2. The comparison pid != targetpid compares an integer with a string, which is unreliable. The target PID should be explicitly cast to an integer for a safe comparison.
3. Comparing apc_routine as a string to "0x00000000" is brittle. It's more robust to convert it to an integer and check if it's non-zero.

The suggested change addresses these issues by ensuring targetpid exists, performing a safe type conversion, and using a more robust check for apc_routine.

Suggested change

	targetpid = self.get_argument(call, "ProcessId")
	if str(apc_routine) != "0x00000000" and pid != targetpid:
	if target_thread not in self.apc_targets:
	self.apc_targets.add(target_thread)
	self.mark_call()
	self.ret = True
	targetpid_str = self.get_argument(call, "ProcessId")
	if targetpid_str and int(apc_routine, 16) != 0:
	targetpid = int(targetpid_str)
	if pid != targetpid:
	if target_thread not in self.apc_targets:
	self.apc_targets.add(target_thread)
	self.mark_call()
	self.ret = True

[gemini-code-assist]

There is trailing whitespace on line 83 and an unnecessary blank line on line 85. These should be removed to improve code style and readability.

Suggested change

	target_thread = self.get_argument(call, "ThreadHandle")
	apc_routine = self.get_argument(call, "pfnAPC")
	target_thread = self.get_argument(call, "ThreadHandle")
	apc_routine = self.get_argument(call, "pfnAPC")