Cloudflared Tunnel Execution

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Janantha Marasinghe, Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

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.

Known false positives

Legitimate usage of Cloudflared tunnel.

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1090` Proxy `T1102` Web Service `T1572` Protocol Tunneling

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

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

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    CommandLine|contains|all:
        - ' tunnel '
        - ' run '
    CommandLine|contains:
        - '-config '
        - '-credentials-contents '
        - '-credentials-file '
        - '-token '

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`run` corpus 2 (sigma 2) `tunnel` corpus 3 (sigma 3) `-config` corpus 3 (sigma 3) `-credentials-contents` corpus 2 (sigma 2) `-credentials-file` corpus 2 (sigma 2) `-token` corpus 2 (sigma 2)	`field:"CommandLine" kind:match`