Malicious Koi Loader Scheduled Task Masquerading as Firefox Agent (via process_creation)

ATT&CK techniques

Execution → Priv Esc

Recon
Resource Dev
Initial Access
Execution
- T1053.005Scheduled Task
Persistence
- T1053.005Scheduled Task
Priv Esc
- T1053.005Scheduled Task
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects creation of a scheduled task named Firefox Default Browser Agent that launches wscript, the persistence trick used by Koi Loader to run agent.js under a legitimate-sounding Mozilla task name. The genuine Firefox task executes default-browser-agent.exe rather than a script host, so a wscript action is false context. Koi Loader is a precursor to the Koi Stealer.

Reporting behind it

Related detections9 linkedT1053.005 — drag to rearrange

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Suspicious Per-Minute SYSTEM Scheduled Task With Highest Privileges

Malicious Koi Loader Scheduled Task Masquerading as Firefox Agent (via process_creation)

Pivot detection · T1053.005 · 9 related

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

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