HTTP Malware User Agent

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

This Splunk query analyzes web logs to identify and categorize user agents, detecting various types of malware. This activity can signify possible compromised hosts on the network.

name: HTTP Malware User Agent
id: 8c4866e4-f488-4253-8537-7dc4f954c292
version: 5
creation_date: '2026-01-06'
modification_date: '2026-05-13'
author: Raven Tait, Splunk
status: production
type: TTP
description: This Splunk query analyzes web logs to identify and categorize user agents, detecting various types of malware. 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 malware_user_agents malware_user_agent AS http_user_agent OUTPUT malware
    | where isnotnull(malware)
    | stats count min(firstTime) as first_seen max(lastTime) as last_seen
      BY malware url http_user_agent
         src dest
    | `security_content_ctime(first_seen)`
    | `security_content_ctime(last_seen)`
    | `http_malware_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: Filtering may be required in some instances depending on legacy system usage, filter as needed.
references:
    - https://github.com/mthcht/awesome-lists/blob/main/Lists/suspicious_http_user_agents_list.csv
drilldown_searches:
    - name: View the detection results for - "$src$"
      search: '%original_detection_search% | search  src = "$src$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$src$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$src$") | 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: A known malware user agent $http_user_agent$ was performing a request from $src$.
    entity:
        field: src
        type: system
        score: 50
threat_objects:
    - field: http_user_agent
      type: http_user_agent
analytic_story:
    - Lokibot
    - Lumma Stealer
    - Meduza Stealer
    - Crypto Stealer
    - RedLine Stealer
    - Suspicious User Agents
asset_type: Network
mitre_attack_id:
    - T1071.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: network
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1071.001/http_user_agents/suricata_malware.log
          sourcetype: suricata
          source: not_applicable
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

3b9dc318-a96d-47be-bf01-1fb4e62c5801

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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