[Rule Tuning] File Transfer or Listener Established via Netcat

[Aegrah]

Summary

Tuning this rule to ensure it is not bypassed through double command-line flag usage.

[github-actions]

Rule: Tuning - Guidelines

These guidelines serve as a reminder set of considerations when tuning an existing rule.

Documentation and Context

• Detailed description of the suggested changes.
• Provide example JSON data or screenshots.
• Provide evidence of reducing benign events mistakenly identified as threats (False Positives).
• Provide evidence of enhancing detection of true threats that were previously missed (False Negatives).
• Provide evidence of optimizing resource consumption and execution time of detection rules (Performance).
• Provide evidence of specific environment factors influencing customized rule tuning (Contextual Tuning).
• Provide evidence of improvements made by modifying sensitivity by changing alert triggering thresholds (Threshold Adjustments).
• Provide evidence of refining rules to better detect deviations from typical behavior (Behavioral Tuning).
• Provide evidence of improvements of adjusting rules based on time-based patterns (Temporal Tuning).
• Provide reasoning of adjusting priority or severity levels of alerts (Severity Tuning).
• Provide evidence of improving quality integrity of our data used by detection rules (Data Quality).
• Ensure the tuning includes necessary updates to the release documentation and versioning.

Rule Metadata Checks

• updated_date matches the date of tuning PR merged.
• min_stack_version should support the widest stack versions.
• name and description should be descriptive and not include typos.
• query should be inclusive, not overly exclusive. Review to ensure the original intent of the rule is maintained.

Testing and Validation

• Validate that the tuned rule's performance is satisfactory and does not negatively impact the stack.
• Ensure that the tuned rule has a low false positive rate.

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ File Transfer or Listener Established via Netcat (eql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[tradebot-elastic]

⛔️ Test failed

Results

• ❌ File Transfer or Listener Established via Netcat (eql)
  • coverage_issue: no_rta
  • stack_validation_failed: no_rta

[Samirbous]

is the network event is really necessary here ? (the 1st event of the seq should be enough to triage and less performance req)

process where host.os.type == "linux" and event.type == "start" and 
      process.name in ("nc","ncat","netcat","netcat.openbsd","netcat.traditional") and (
          /* bind shell to specific port or listener */
          process.args:("-*l*","-*p*")
          /* reverse shell to command-line interpreter used for command execution */
          or (process.args: "-e" and process.args:("/bin/bash","/bin/sh"))
          /* file transfer via stdout */
          or process.args:(">","<")
          /* file transfer via pipe */
          or (process.args:("|") and process.args:("nc","ncat"))
      ) and
      not process.command_line like~ ("*127.0.0.1*", "*localhost*")

[Samirbous]

Suggested change

	sequence by process.entity_id with maxspan=1m
	[process where host.os.type == "linux" and event.type == "start"
	process.name in ("nc","ncat","netcat","netcat.openbsd","netcat.traditional") and (
	/* bind shell to specific port or listener */
	or process.args:("-*l*","-*p*")
	sequence by process.entity_id with maxspan=1m
	[process where host.os.type == "linux" and event.type == "start" and
	process.name in ("nc","ncat","netcat","netcat.openbsd","netcat.traditional") and (
	/* bind shell to specific port or listener */
	process.args:("-*l*","-*p*")