Suspicious Unblock-File

Remove the Zone.Identifier alternate data stream which identifies the file as downloaded from the internet.

Sigma rule (View on GitHub)

 1title: Suspicious Unblock-File
 2id: 5947497f-1aa4-41dd-9693-c9848d58727d
 3status: test
 4description: Remove the Zone.Identifier alternate data stream which identifies the file as downloaded from the internet.
 5references:
 6    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1553.005/T1553.005.md#atomic-test-3---remove-the-zoneidentifier-alternate-data-stream
 7    - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/unblock-file?view=powershell-7.2
 8author: frack113
 9date: 2022/02/01
10tags:
11    - attack.defense_evasion
12    - attack.t1553.005
13logsource:
14    product: windows
15    category: ps_script
16    definition: 'Requirements: Script Block Logging must be enabled'
17detection:
18    selection:
19        ScriptBlockText|contains|all:
20            - 'Unblock-File '
21            - '-Path '
22    condition: selection
23falsepositives:
24    - Legitimate PowerShell scripts
25level: medium

References

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