Malicious IIS Worker Spawning nslookup via WS_FTP Deserialization

ATT&CK techniques

Initial Access → Execution

Recon
Resource Dev
Initial Access
- T1190Exploit Public-Facing Application
Execution
- T1059.003Windows Command Shell
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects the IIS worker process w3wp.exe spawning cmd.exe to run nslookup, matching the out-of-band verification step in the WS_FTP Ad Hoc deserialization exploit for CVE-2023-40044 shown by Assetnote. A web worker executing shell commands that resolve attacker-controlled hostnames indicates code execution through the vulnerable HTTP module. Such a process chain from IIS is rarely legitimate and points to active exploitation.

Reporting behind it

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Malicious IIS Worker Spawning nslookup via WS_FTP Deserialization

Pivot detection · T1059.003 · 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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