AWL Bypass with Winrm.vbs and Malicious WsmPty.xsl/WsmTxt.xsl - File

Severity: medium
Author: Julia Fomina, oscd.community
Source: upstream

Detects execution of attacker-controlled WsmPty.xsl or WsmTxt.xsl via winrm.vbs and copied cscript.exe (can be renamed)

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1216` System Script Proxy Execution

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `system_files`

or:
TargetFilename|endswith: WsmPty.xsl
TargetFilename|endswith: WsmTxt.xsl

Stage 2: `not in_system_folder`

or:
TargetFilename|startswith: 'C:\Windows\SysWOW64\'
TargetFilename|startswith: 'C:\Windows\System32\'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`TargetFilename`	ends_with	`WsmPty.xsl` `WsmTxt.xsl`
`TargetFilename`	starts_with	`C:\Windows\SysWOW64\` corpus 2 (sigma 2) `C:\Windows\System32\` corpus 3 (sigma 3)