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

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	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `contains_winrm`

CommandLine|contains: winrm

Stage 2: `contains_format_pretty_arg`

or:
CommandLine|contains: 'format:"pretty"'
CommandLine|contains: 'format:"text"'
CommandLine|contains: 'format:pretty'
CommandLine|contains: 'format:text'

Stage 3: `not image_from_system_folder`

or:
Image|startswith: 'C:\Windows\SysWOW64\'
Image|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
`CommandLine`	match	`format:"pretty"` `format:"text"` `format:pretty` `format:text` `winrm` corpus 2 (sigma 2)
`Image`	starts_with	`C:\Windows\SysWOW64\` corpus 16 (sigma 16) `C:\Windows\System32\` corpus 16 (sigma 16)