Malicious Certutil Decode of Encoded Web Shell to ASPX (via process_creation)

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1140Deobfuscate/Decode Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects certutil.exe decoding a text file into an ASPX web shell within a web server images directory as seen in the targeted MS-SQL server intrusion. Certutil decoding output directly into a web accessible aspx file is a common web shell deployment technique.

Reporting behind it

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Certutil Decoding Encoded Payload to Executable

Malicious Certutil Decode of Encoded Web Shell to ASPX (via process_creation)

Pivot detection · T1140 · 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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