HTTP PUA User Agent

name: HTTP PUA User Agent
id: 21af5447-734f-4549-956b-7a255cb2b032
version: 5
creation_date: '2026-01-06'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: Anomaly
description: This Splunk query analyzes web logs to identify and categorize user agents, detecting various types of unwanted applications. This activity can signify possible compromised hosts on the network.
data_source:
    - Suricata
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Web
      WHERE Web.http_user_agent != null
      BY Web.http_user_agent Web.http_method, Web.url,
         Web.url_length Web.src, Web.dest
    | `drop_dm_object_name("Web")`
    | lookup pua_user_agents pua_user_agent AS http_user_agent OUTPUT tool
    | where isnotnull(tool)
    | stats count min(firstTime) as first_seen max(lastTime) as last_seen
      BY tool url http_user_agent
         src dest
    | `security_content_ctime(first_seen)`
    | `security_content_ctime(last_seen)`
    | `http_pua_user_agent_filter`
how_to_implement: To successfully implement this search, you need to be ingesting web or proxy logs, or ensure it is being filled by a proxy like device, into the Web Datamodel. For additional filtering, allow list private IP space or restrict by known good.
known_false_positives: Noise and false positive can be seen if these programs are allowed to be used within corporate network. In this case, a filter is needed.
references:
    - https://github.com/mthcht/awesome-lists/blob/main/Lists/suspicious_http_user_agents_list.csv
intermediate_findings:
    entities:
        - field: src
          type: system
          score: 20
          message: A known user agent ($http_user_agent$) associated with unusual programs was performing a request from $src$.
threat_objects:
    - field: http_user_agent
      type: http_user_agent
analytic_story:
    - Local Privilege Escalation With KrbRelayUp
    - BlackSuit Ransomware
    - Cactus Ransomware
    - Suspicious User Agents
asset_type: Network
mitre_attack_id:
    - T1071.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network