Suspicious which Enumeration

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This rule monitors for the usage of the which command with an unusual amount of process arguments. Attackers may leverage the which command to enumerate the system for useful installed utilities that may be used after compromising a system to escalate privileges or move latteraly across the network.

Rule type: eql

Rule indices:

  • logs-endpoint.events.*

Severity: low

Risk score: 21

Runs every: 60m

Searches indices from: now-119m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Discovery
  • Data Source: Elastic Defend
  • Rule Type: BBR

Version: 2

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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process where host.os.type == "linux" and event.action == "exec" and event.type == "start" and
process.name == "which" and process.args_count >= 10

/* potential tuning if rule would turn out to be noisy
and process.args in ("nmap", "nc", "ncat", "netcat", nc.traditional", "gcc", "g++", "socat") and
process.parent.name in ("bash", "dash", "ash", "sh", "tcsh", "csh", "zsh", "ksh", "fish")
*/

Framework: MITRE ATT&CKTM