Suspicious Kernel Feature Activity

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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*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: now-9m (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: Defense Evasion
Tactic: Discovery
Data Source: Elastic Defend

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

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 // also detects --append
  (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 *")
)

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Impair Defenses
- ID: T1562
- Reference URL: https://attack.mitre.org/techniques/T1562/
Sub-technique:
- Name: Indicator Blocking
- ID: T1562.006
- Reference URL: https://attack.mitre.org/techniques/T1562/006/
Technique:
- Name: Subvert Trust Controls
- ID: T1553
- Reference URL: https://attack.mitre.org/techniques/T1553/
Tactic:
- Name: Discovery
- ID: TA0007
- Reference URL: https://attack.mitre.org/tactics/TA0007/
Technique:
- Name: System Information Discovery
- ID: T1082
- Reference URL: https://attack.mitre.org/techniques/T1082/

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