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Suspicious Kernel Feature Activity

This rule detects the modification and reading of kernel features through built-in commands. Attackers may collect information, disable or weaken Linux kernel protections. For example, an attacker may modify ASLR protection by disabling kernel.randomize_va_space, allow ptrace by setting kernel.yama.ptrace_scope to 0, or disable the NMI watchdog by setting kernel.nmi_watchdog to 0. These changes may be used to impair defenses and evade detection.

Rule type: eql
Rule indices:

  • logs-endpoint.events.process*

Rule Severity: low
Risk Score: 21
Runs every:
Searches indices from: now-9m
Maximum alerts per execution: ?
References:

Tags:

  • Domain: Endpoint
  • OS: Linux
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Tactic: Discovery
  • Data Source: Elastic Defend

Version: ?
Rule authors:

  • Elastic

Rule license: Elastic License v2

process where host.os.type == "linux" and event.type == "start" and event.action == "exec" and
process.command_line : (
  "*/etc/sysctl.conf*", "*/etc/sysctl.d/*", "*/proc/sys/kernel/nmi_watchdog*",
  "*/proc/sys/vm/nr_hugepages*", "*/proc/sys/kernel/yama/ptrace_scope*",
  "*/proc/sys/kernel/randomize_va_space*", "*/proc/sys/vm/drop_caches*",
  "*/proc/sys/kernel/sysrq*", "*grsecurity*", "*exec-shield*",
  "*kernel.randomize_va_space*", "*kernel.yama.ptrace_scope*",
  "*kernel.nmi_watchdog*", "*vm.nr_hugepages*", "*vm.drop_caches*",
  "*kernel.sysrq*"
) and
process.parent.executable != null and
(
  (process.name == "tee" and process.args like "-*a*") or
  (process.name == "cat" and not process.parent.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish")) or
  (process.name == "grep" and process.args_count == 3 and not process.parent.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish")) or
  (process.name == "sysctl" and process.args like ("*-w*", "*--write*", "*=*")) or
  (process.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and process.args == "-c" and process.args : "*echo *")
)
  1. also detects --append

Framework: MITRE ATT&CK

Framework: MITRE ATT&CK