BabyShark Agent Default C2 URL Query String Pattern (Proxy Logs)

Alerts on proxy URIs containing the BabyShark agent default "momyshark?key=" query pattern.

FreeUnreviewedSigmacriticalv1

babyshark-agent-default-c2-url-query-string-pattern-proxy-logs-304810ed

title: BabyShark Agent Default C2 URL Query String Pattern (Proxy Logs)
id: db397d15-66e5-4aeb-bcd6-f32afccc4dba
status: test
description: This rule flags proxy requests whose URL path contains the BabyShark agent default query pattern "momyshark?key=". Such a distinctive C2 beaconing format can indicate automated command-and-control traffic from an implant. The detection relies on proxy telemetry that records the full request URI, matching on the presence of the specific substring.
references:
  - https://nasbench.medium.com/understanding-detecting-c2-frameworks-babyshark-641be4595845
  - https://github.com/SigmaHQ/sigma/blob/master/rules/web/proxy_generic/proxy_hktl_baby_shark_default_agent_url.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2021-06-09
modified: 2024-02-15
tags:
  - attack.command-and-control
  - attack.t1071.001
logsource:
  category: proxy
detection:
  selection:
    c-uri|contains: momyshark\?key=
  condition: selection
falsepositives:
  - Unlikely
level: critical
license: DRL-1.1
related:
  - id: 304810ed-8853-437f-9e36-c4975c3dfd7e
    type: derived

What it detects

This rule flags proxy requests whose URL path contains the BabyShark agent default query pattern "momyshark?key=". Such a distinctive C2 beaconing format can indicate automated command-and-control traffic from an implant. The detection relies on proxy telemetry that records the full request URI, matching on the presence of the specific substring.

Known false positives

Unlikely

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.