NET NGenAssemblyUsageLog Registry Key Tamper

calendar Oct 23, 2025 · attack.persistence attack.defense-evasion attack.t1112  ·
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Detects changes to the NGenAssemblyUsageLog registry key. .NET Usage Log output location can be controlled by setting the NGenAssemblyUsageLog CLR configuration knob in the Registry or by configuring an environment variable (as described in the next section). By simplify specifying an arbitrary value (e.g. fake output location or junk data) for the expected value, a Usage Log file for the .NET execution context will not be created.

Sigma rule (View on GitHub)

 1title: NET NGenAssemblyUsageLog Registry Key Tamper
 2id: 28036918-04d3-423d-91c0-55ecf99fb892
 3status: test
 4description: |
 5  Detects changes to the NGenAssemblyUsageLog registry key.
 6  .NET Usage Log output location can be controlled by setting the NGenAssemblyUsageLog CLR configuration knob in the Registry or by configuring an environment variable (as described in the next section).
 7  By simplify specifying an arbitrary value (e.g. fake output location or junk data) for the expected value, a Usage Log file for the .NET execution context will not be created.  
 8references:
 9    - https://bohops.com/2021/03/16/investigating-net-clr-usage-log-tampering-techniques-for-edr-evasion/
10author: frack113
11date: 2022-11-18
12modified: 2023-08-17
13tags:
14    - attack.persistence
15    - attack.defense-evasion
16    - attack.t1112
17logsource:
18    product: windows
19    category: registry_set
20detection:
21    selection:
22        TargetObject|endswith: 'SOFTWARE\Microsoft\.NETFramework\NGenAssemblyUsageLog'
23    condition: selection
24falsepositives:
25    - Unknown
26level: high

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