Apache Guacamole Linux: Two-User Session Presence Anomaly
Flags Guacamole sessions on Linux when telemetry indicates two users are present, suggesting anomalous or suspicious session activity.
- Product
- linux
- Service
- guacamole
- Author
- Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2020-07-03
- Updated
- 2026-07-31
ATT&CK techniques
Cred AccessRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags a suspicious Guacamole session state where the system indicates two users are now present. Such behavior can be consistent with unauthorized access or session takeover, since an attacker may cause additional user presence within an active session. It relies on Guacamole service telemetry that reports the '(2 users now present)' session anomaly indicator on Linux.
Reporting behind it
Changelog
v3- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No 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.
title: "Apache Guacamole Linux: Two-User Session Presence Anomaly"
id: b1889dd4-c570-4a65-a03a-83e3e6d84631
status: test
description: This rule flags a suspicious Guacamole session state where the system indicates two users are now present. Such behavior can be consistent with unauthorized access or session takeover, since an attacker may cause additional user presence within an active session. It relies on Guacamole service telemetry that reports the '(2 users now present)' session anomaly indicator on Linux.
references:
- https://research.checkpoint.com/2020/apache-guacamole-rce/
- https://github.com/SigmaHQ/sigma/blob/master/rules/linux/builtin/guacamole/lnx_guacamole_susp_guacamole.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2020-07-03
modified: 2021-11-27
tags:
- attack.credential-access
- attack.t1212
logsource:
product: linux
service: guacamole
detection:
selection:
- (2 users now present)
condition: selection
falsepositives:
- Unknown
level: high
license: DRL-1.1
related:
- id: 1edd77db-0669-4fef-9598-165bda82826d
type: derived