Linux Possible System Binary Backdoor

SPLUNK detection rule by Raven Tait, Splunk · Apache-2.0

The following analytic detects the creation or overwrite of commonly targeted Linux system binaries such as cat, ls, cp, ps, mv, netstat, ss, and lsof. Adversaries may replace these utilities with backdoored versions to hide malicious activity, harvest credentials, or maintain persistence while appearing to use legitimate system tools. This technique is associated with rootkit deployment and post-exploitation frameworks such as PANIX.

name: Linux Possible System Binary Backdoor
id: a806d611-ea81-4d8a-9b9b-fbf5b6ec520a
version: 1
creation_date: '2026-07-08'
modification_date: '2026-07-08'
author: Raven Tait, Splunk
status: production
type: Anomaly
description: |-
    The following analytic detects the creation or overwrite of commonly targeted Linux system binaries such as cat, ls, cp, ps, mv, netstat, ss, and lsof.
    Adversaries may replace these utilities with backdoored versions to hide malicious activity, harvest credentials, or maintain persistence while appearing to use legitimate system tools.
    This technique is associated with rootkit deployment and post-exploitation frameworks such as PANIX.
data_source:
    - Sysmon for Linux EventID 11
search: |-
    | tstats `security_content_summariesonly`
      count min(_time) as firstTime max(_time) as lastTime

    from datamodel=Endpoint.Filesystem where

    Filesystem.file_path IN (
        "/usr/bin/cat",
        "/usr/bin/cp",
        "/usr/bin/ls",
        "/usr/bin/lsof",
        "/usr/bin/mv",
        "/usr/bin/netstat",
        "/usr/bin/ps",
        "/usr/bin/ss"
    )

    by Filesystem.file_path Filesystem.file_name Filesystem.user Filesystem.dest
       Filesystem.action Filesystem.process_guid Filesystem.process_id

    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `linux_possible_system_binary_backdoor_filter`
how_to_implement: |-
    The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain file creation events including the file path and user context. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Filesystem` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
known_false_positives: |-
    Legitimate system updates or package managers may create or overwrite system binaries during normal operations. Filter for known update processes and package management activity to reduce noise.
references:
    - https://github.com/Aegrah/PANIX
drilldown_searches:
    - earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
      name: View the detection results for - "$user$" and "$dest$"
      search: '%original_detection_search% | search  user = "$user$" dest = "$dest$"'
    - name: View risk events for the last 7 days for - "$user$" and "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$dest$") | 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'
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: Possible System Binary Backdoor activity observed on [$dest$]. System binary [$file_name$] was created or overwritten by [$user$].
threat_objects:
    - field: file_name
      type: file_name
analytic_story:
    - Linux Post-Exploitation
    - Linux Persistence Techniques
    - Linux Privilege Escalation
    - Compromised Linux Host
asset_type: Endpoint
mitre_attack_id:
    - T1036
    - T1059.004
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      test_type: unit
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1036/linux_possible_system_binary_backdoor/snapattack_linux.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux

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