Cloudflared Tunnel Execution — Sigma Rule

Rule metadata and linked tags

Author: Janantha Marasinghe, Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2023-05-17 / 2023-12-20.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 537ccfd832d9322aeae597a755d94d161caf81d0514f494a505a21099d6af511

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Cloudflared Tunnel Execution
id: 9a019ffc-3580-4c9d-8d87-079f7e8d3fd4
status: test
description: Detects execution of the "cloudflared" tool to connect back to a tunnel. This was seen used by threat actors to maintain persistence and remote access to compromised networks.
references:
    - https://blog.reconinfosec.com/emergence-of-akira-ransomware-group
    - https://github.com/cloudflare/cloudflared
    - https://developers.cloudflare.com/cloudflare-one/connections/connect-apps
author: Janantha Marasinghe, Nasreddine Bencherchali (Nextron Systems)
date: 2023-05-17
modified: 2023-12-20
tags:
    - attack.command-and-control
    - attack.t1102
    - attack.t1090
    - attack.t1572
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains|all:
            - ' tunnel '
            - ' run '
        CommandLine|contains:
            - '-config '
            - '-credentials-contents '
            - '-credentials-file '
            - '-token '
    condition: selection
falsepositives:
    - Legitimate usage of Cloudflared tunnel.
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate usage of Cloudflared tunnel.

Source references

• https://blog.reconinfosec.com/emergence-of-akira-ransomware-group
• https://github.com/cloudflare/cloudflared
• https://developers.cloudflare.com/cloudflare-one/connections/connect-apps