Testing Usage of Uncommonly Used Port

Adversaries may communicate using a protocol and port paring that are typically not associated. For example, HTTPS over port 8088(Citation: Symantec Elfin Mar 2019) or port 587(Citation: Fortinet Agent Tesla April 2018) as opposed to the traditional port 443.

Sigma rule (View on GitHub)

 1title: Testing Usage of Uncommonly Used Port
 2id: adf876b3-f1f8-4aa9-a4e4-a64106feec06
 3status: test
 4description: |
 5    Adversaries may communicate using a protocol and port paring that are typically not associated.
 6    For example, HTTPS over port 8088(Citation: Symantec Elfin Mar 2019) or port 587(Citation: Fortinet Agent Tesla April 2018) as opposed to the traditional port 443.    
 7references:
 8    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1571/T1571.md#atomic-test-1---testing-usage-of-uncommonly-used-port-with-powershell
 9    - https://learn.microsoft.com/en-us/powershell/module/nettcpip/test-netconnection?view=windowsserver2022-ps
10author: frack113
11date: 2022/01/23
12tags:
13    - attack.command_and_control
14    - attack.t1571
15logsource:
16    product: windows
17    category: ps_script
18    definition: 'Requirements: Script Block Logging must be enabled'
19detection:
20    selection:
21        ScriptBlockText|contains|all:
22            - Test-NetConnection
23            - '-ComputerName '
24            - '-port '
25    filter:
26        ScriptBlockText|contains:
27            - ' 443 '
28            - ' 80 '
29    condition: selection and not filter
30falsepositives:
31    - Legitimate administrative script
32level: medium

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