Sigma rule: Registry Set With Crypto-Classes From The "Cryptography" PowerShell Namespace

Rule

Title

Registry Set With Crypto-Classes From The "Cryptography" PowerShell Namespace

Status

test

Level

medium

Author

Andreas Braathen (mnemonic.io)

Date

2023-12-01

File

rules-threat-hunting/windows/registry/registry_set/registry_set_powershell_crypto_namespace.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects the setting of a registry inside the "\Shell\Open\Command" value with PowerShell classes from the "System.Security.Cryptography" namespace.
The PowerShell namespace "System.Security.Cryptography" provides classes for on-the-fly encryption and decryption.
These can be used for example in decrypting malicious payload for defense evasion.

Log source

product

windows

category

registry_set

Detection

selection_key:
    TargetObject|contains: '\Shell\Open\Command'
selection_value_img:
    Details|contains:
        - 'powershell'
        - 'pwsh'
selection_value_namespace:
    Details|contains: 'System.Security.Cryptography.'
selection_value_classes:
    Details|contains:
        - '.AesCryptoServiceProvider'
        - '.DESCryptoServiceProvider'
        - '.DSACryptoServiceProvider'
        - '.RC2CryptoServiceProvider'
        - '.Rijndael'
        - '.RSACryptoServiceProvider'
        - '.TripleDESCryptoServiceProvider'
condition: all of selection_*

False positives (as the rule lists them)

• Classes are legitimately used, but less so when e.g. parents with low prevalence or decryption of content in temporary folders.

Tags

• attack.execution
• attack.persistence
• attack.privilege-escalation
• attack.stealth
• attack.t1059.001
• attack.t1027.010
• attack.t1547.001
• detection.threat-hunting

MITRE ATT&CK ids this rule names

• T1027.010
• T1059.001
• T1547.001

References

• https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography?view=net-8.0
• https://squiblydoo.blog/2023/11/07/october-2023-solarmarker/

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-threat-hunting/windows/registry/registry_set/registry_set_powershell_crypto_namespace.yml