Linux Magic SysRq Key Abuse

name: Linux Magic SysRq Key Abuse
id: 22c03600-f84a-47fa-abaa-ffbe3e72c782
version: 5
creation_date: '2025-08-28'
modification_date: '2026-05-13'
author: Milad Cheraghi
status: production
type: TTP
description: |
    Detects potential abuse of the Linux Magic SysRq (System Request) key by adversaries with root or sufficient privileges to manipulate or destabilize a system.
    Writing to /proc/sysrq-trigger can crash the system, kill processes, or bypass standard logging.
    Monitoring SysRq abuse helps detect stealthy post-exploitation activity.
    Correlate with related EXECVE or PROCTITLE events to identify the process or user responsible for the access or modification.
data_source:
    - Linux Auditd Path
    - Linux Auditd Cwd
search: |
    `linux_auditd`
    (type=PATH OR type=CWD)
    | rex "msg=audit\([^)]*:(?<audit_id>\d+)\)"

    | stats
      values(type) as types
      values(name) as names
      values(nametype) as nametype
      values(cwd) as cwd_list
      values(_time) as event_times
      by audit_id, host

    | eval current_working_directory = coalesce(mvindex(cwd_list, 0), "N/A")
    | eval candidate_paths = mvmap(names, if(match(names, "^/"), names, current_working_directory + "/" + names))
    | eval matched_paths = mvfilter(match(candidate_paths, ".*/proc/sysrq-trigger|.*/proc/sys/kernel/sysrq|.*/etc/sysctl.conf"))
    | eval match_count = mvcount(matched_paths)
    | eval reconstructed_path = mvindex(matched_paths, 0)
    | eval e_time = mvindex(event_times, 0)
    | where match_count > 0
    | rename host as dest

    | stats count min(e_time) as firstTime max(e_time) as lastTime
      values(nametype) as nametype
      by current_working_directory
         reconstructed_path
         match_count
         dest
         audit_id

    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `linux_magic_sysrq_key_abuse_filter`
how_to_implement: |
    To implement this detection, ensure auditd is configured to watch:
      - /proc/sysrq-trigger
      - /proc/sys/kernel/sysrq
      - /etc/sysctl.conf
    with write and attribute changes (`-p wa`) and key `sysrq`. Make sure the type=CWD record type is activate in your auditd configuration and
    Use the Splunk Add-on for Unix and Linux for proper ingestion and CIM normalization.
    This enables effective monitoring of Linux endpoints for SysRq abuse.
known_false_positives: |
    Legitimate administrative activity modifying SysRq for debugging or recovery.
    Please update the filter macros to remove false positives.
references:
    - https://www.kernel.org/doc/html/v4.10/_sources/admin-guide/sysrq.txt
    - https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/4/html/reference_guide/s3-proc-sys-kernel
    - https://www.splunk.com/en_us/blog/security/threat-update-awfulshred-script-wiper.html
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search dest="$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: Abuse of the Linux Magic System Request key detected on host - [$dest$]
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Compromised Linux Host
asset_type: Endpoint
mitre_attack_id:
    - T1059.004
    - T1529
    - T1489
    - T1499
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1529/auditd_path_sysrq/path_sysrq.log
          source: auditd
          sourcetype: auditd
      test_type: unit