huntrule

Linux: Shell spawned by rsync without -e flag in command line

Flags rsync/rsyncd spawning a shell when rsync lacks the expected " -e " command-line flag.

FreeReviewedSigma · High · v2
Product
linux
Category
process_creation
Author
Florian Roth (SigmaHQ), DRL 1.1
Published
2025-01-18
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies process creation where a shell executable (e.g., sh, bash, dash) is launched as a child of rsync (rsync/rsyncd) while the rsync command line does not contain the expected ' -e ' flag. Spawning a shell from a file transfer utility is a strong indicator of misuse, such as remote command execution or exploitation attempts leading to unauthorized actions. It relies on Linux process creation telemetry, specifically parent/child process image paths and command-line content.

Reporting behind it

Related detections9 linkedT1059 — drag to rearrange
Windows: Suspicious Script/Command Child Processes Spawned by ArcSOC.exe
Suspicious Child Processes Spawned by Browsers on macOS
Malicious Web Server Process Spawning Command Interpreter via Web Shell (via process_creation)
Suspicious VMware Guest Operation Output Staging in vmware-system Temp Directory (via file_event)
Malicious Command Shell Spawned by SQL Server via Process Creation (via process_creation)
Suspicious Script Interpreter Spawned by Excel via DarkGate Lure
Suspicious AutoHotkey Script Execution from User Writable Path by DarkGate
Malicious China Chopper Web Shell Command Pattern in IIS Worker Process (via process_creation)
Malicious AutoHotKey Runner AutoNotify Executing AHKBot Looper Script (via process_creation)
Linux: Shell spawned by rsync without -e flag in command line
Pivot detection · T1059 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. 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.