Sigma rule: Change User Agents with WebRequest

Rule

Title

Change User Agents with WebRequest

Status

test

Level

medium

Author

frack113

Date

2022-01-23

Modified

2025-07-18

File

rules/windows/powershell/powershell_script/posh_ps_susp_invoke_webrequest_useragent.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Adversaries may communicate using application layer protocols associated with web traffic to avoid detection/network filtering by blending in with existing traffic.
Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

Log source

product

windows

category

ps_script

definition

Requirements: Script Block Logging must be enabled

Detection

selection_webrequest:
    ScriptBlockText|contains:
        - 'Invoke-WebRequest'
        - 'Invoke-RestMethod'
        - ' irm ' # Space before and after to avoid false positives with 'irm' as a variable
        - 'iwr '
selection_useragent:
    ScriptBlockText|contains: '-UserAgent '
condition: all of selection_*

False positives (as the rule lists them)

• Unknown

Tags

• attack.command-and-control
• attack.t1071.001

MITRE ATT&CK ids this rule names

• T1071.001

References

• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1071.001/T1071.001.md#t1071001---web-protocols

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_susp_invoke_webrequest_useragent.yml