PUA - Fast Reverse Proxy (FRP) Execution

Hunt Hypothesis

Detects the use of Fast Reverse Proxy. frp is a fast reverse proxy to help you expose a local server behind a NAT or firewall to the Internet.

Detection Rule

Sigma (Original)

title: PUA - Fast Reverse Proxy (FRP) Execution
id: 32410e29-5f94-4568-b6a3-d91a8adad863
status: test
description: Detects the use of Fast Reverse Proxy. frp is a fast reverse proxy to help you expose a local server behind a NAT or firewall to the Internet.
references:
    - https://asec.ahnlab.com/en/38156/
    - https://github.com/fatedier/frp
author: frack113, Florian Roth
date: 2022-09-02
modified: 2024-11-23
tags:
    - attack.command-and-control
    - attack.t1090
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        Image|endswith:
            - '\frpc.exe'
            - '\frps.exe'
    selection_cli:
        CommandLine|contains: '\frpc.ini'
    selection_hashes:
        # v0.44.0
        Hashes|contains:
            - "MD5=7D9C233B8C9E3F0EA290D2B84593C842"
            - "SHA1=06DDC9280E1F1810677935A2477012960905942F"
            - "SHA256=57B0936B8D336D8E981C169466A15A5FD21A7D5A2C7DAF62D5E142EE860E387C"
    condition: 1 of selection_*
falsepositives:
    - Legitimate use
level: high

KQL (Azure Sentinel)

imProcessCreate
| where (TargetProcessName endswith "\\frpc.exe" or TargetProcessName endswith "\\frps.exe") or TargetProcessCommandLine contains "\\frpc.ini" or (TargetProcessMD5 startswith "7D9C233B8C9E3F0EA290D2B84593C842" or TargetProcessSHA1 startswith "06DDC9280E1F1810677935A2477012960905942F" or TargetProcessSHA256 startswith "57B0936B8D336D8E981C169466A15A5FD21A7D5A2C7DAF62D5E142EE860E387C")

Required Data Sources

False Positive Guidance

• Legitimate use

MITRE ATT&CK Context

• Tactic: Command and Control
• Technique: T1090 — T1090

References

• https://asec.ahnlab.com/en/38156/
• https://github.com/fatedier/frp
• SigmaHQ Rule