Sigma rule: Suspicious Execution of Powershell with Base64

Rule

Title

Suspicious Execution of Powershell with Base64

Status

test

Level

medium

Author

frack113

Date

2022-01-02

Modified

2023-01-05

File

rules/windows/process_creation/proc_creation_win_powershell_encode.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Commandline to launch powershell with a base64 payload

Log source

product

windows

category

process_creation

Detection

selection:
    Image|endswith:
        - \powershell.exe
        - \pwsh.exe
    CommandLine|contains:
        - ' -e '
        - ' -en '
        - ' -enc '
        - ' -enco'
        - ' -ec '
filter_encoding:
    CommandLine|contains: ' -Encoding '
filter_azure:
    ParentImage|contains:
        - 'C:\Packages\Plugins\Microsoft.GuestConfiguration.ConfigurationforWindows\'
        - '\gc_worker.exe'
condition: selection and not 1 of filter_*

False positives (as the rule lists them)

• Unknown

Tags

• attack.execution
• attack.t1059.001

MITRE ATT&CK ids this rule names

• T1059.001

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1059.001/T1059.001.md#atomic-test-20---powershell-invoke-known-malicious-cmdlets
• https://unit42.paloaltonetworks.com/unit42-pulling-back-the-curtains-on-encodedcommand-powershell-attacks/
• https://mikefrobbins.com/2017/06/15/simple-obfuscation-with-powershell-using-base64-encoding/

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