Detect rclone CLI Activity via Proxy User-Agent Prefix

Flags proxy traffic with a user agent beginning with rclone/v, indicating rclone usage through the proxy.

FreeReviewedSigma · Medium · v2

Category: proxy
Author: Janantha Marasinghe (SigmaHQ), DRL 1.1
Published: 2022-10-18
Updated: 2026-07-31

ATT&CK techniques

Exfiltration

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
- T1567.002Exfiltration to Cloud Storage
Impact

What it detects

This rule identifies proxy traffic where the User-Agent begins with the rclone version prefix (rclone/v), indicating rclone may be communicating through a proxy. Such activity matters because rclone is frequently used to automate cloud storage access and can support data transfer and exfiltration workflows. The detection relies on proxy telemetry capturing the HTTP User-Agent header and matches only the specified prefix pattern.

Reporting behind it

Related detections9 linkedT1567.002 — drag to rearrange

Suspicious ALPHA SPIDER Rclone Exfiltration Tool Masquerading as System Binary (via process_creation)

Malicious GhostLocker2 C2 Communication via HTTP POST (via proxy)

Suspicious Rclone Exfiltration Masquerading as wininit.exe

Malicious Bulk Data Exfiltration via Rclone (via process_creation)

Rclone SMB Share Exfiltration

Suspicious Data Exfiltration via Rclone to Cloud Storage (via process_creation)

Malicious Data Exfiltration via MEGAcmd

Suspicious Command and Control via Discord or Telegram Bot API

Data Exfiltration to WebDAV Share via curl Upload

Detect rclone CLI Activity via Proxy User-Agent Prefix

Pivot detection · T1567.002 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

proxy-logs-rclone-user-agent-activity-via-default-rclone-v-prefix-2c03648b

title: Detect rclone CLI Activity via Proxy User-Agent Prefix
id: 684201c3-5457-442f-8751-221af850d92f
status: test
description: This rule identifies proxy traffic where the User-Agent begins with the rclone version prefix (rclone/v), indicating rclone may be communicating through a proxy. Such activity matters because rclone is frequently used to automate cloud storage access and can support data transfer and exfiltration workflows. The detection relies on proxy telemetry capturing the HTTP User-Agent header and matches only the specified prefix pattern.
references:
  - https://rclone.org/
  - https://www.kroll.com/en/insights/publications/cyber/new-m365-business-email-compromise-attacks-with-rclone
  - https://github.com/SigmaHQ/sigma/blob/master/rules/web/proxy_generic/proxy_ua_rclone.yml
author: Janantha Marasinghe, Huntrule Team
date: 2022-10-18
tags:
  - attack.exfiltration
  - attack.t1567.002
logsource:
  category: proxy
detection:
  selection:
    c-useragent|startswith: rclone/v
  condition: selection
falsepositives:
  - Valid requests with this exact user agent to that is used by legitimate scripts or sysadmin operations
level: medium
license: DRL-1.1
related:
  - id: 2c03648b-e081-41a5-b9fb-7d854a915091
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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