Sigma rule: Testing Usage of Uncommonly Used Port

Rule

Title

Testing Usage of Uncommonly Used Port

Status

test

Level

medium

Author

frack113

Date

2022-01-23

File

rules/windows/powershell/powershell_script/posh_ps_test_netconnection.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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.

Log source

product

windows

category

ps_script

definition

Requirements: Script Block Logging must be enabled

Detection

selection:
    ScriptBlockText|contains|all:
        - Test-NetConnection
        - '-ComputerName '
        - '-port '
filter:
    ScriptBlockText|contains:
        - ' 443 '
        - ' 80 '
condition: selection and not filter

False positives (as the rule lists them)

• Legitimate administrative script

Tags

• attack.command-and-control
• attack.t1571

MITRE ATT&CK ids this rule names

• T1571

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1571/T1571.md#atomic-test-1---testing-usage-of-uncommonly-used-port-with-powershell
• https://learn.microsoft.com/en-us/powershell/module/nettcpip/test-netconnection?view=windowsserver2022-ps

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/powershell/powershell_script/posh_ps_test_netconnection.yml