Malicious Script Execution via Cisco AnyConnect OnConnect Handler Abuse

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1059.005Visual Basic
- T1204.002Malicious File
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the Cisco AnyConnect agent or downloader spawning a Windows script host to run OnConnect or OnDisconnect scripts which NCC Group showed can be abused to drop and execute attacker payloads on VPN connect events. Abusing the trusted VPN client for script execution evades application allow lists and provides connection triggered persistence.

Reporting behind it

Related detections9 linkedT1059.005 — drag to rearrange

Suspicious Office Application Spawning Script Interpreter

Suspicious VBScript Execution from Public User Directory (via process_creation)

Malicious LitterDrifter VBScript Execution via wscript trash.dll

Suspicious WScript Execution Spawned by Microsoft Word (via process_creation)

Uncommon Kimsuky OneNote Document Spawning Script Interpreter (via process_creation)

Malicious Excel Macro Spawning Scripting Interpreter Downloader (via process_creation)

Windows AppLocker Audit-Mode Events Indicate Files Would Have Been Blocked

Windows AppLocker Blocked Application, Script, MSI, or Packaged-App Execution

Suspicious VBScript Execution from ProgramLogs Directory via Windows Script Host

Malicious Script Execution via Cisco AnyConnect OnConnect Handler Abuse

Pivot detection · T1059.005 · 9 related

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

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →