Uncommon Child Process Of Appvlp.EXE

Severity: medium
Author: Sreeman
Source: upstream

Detects uncommon child processes of Appvlp.EXE Appvlp or the Application Virtualization Utility is included with Microsoft Office. Attackers are able to abuse "AppVLP" to execute shell commands. Normally, this binary is used for Application Virtualization, but it can also be abused to circumvent the ASR file path rule folder or to mark a file as a system file.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218` System Binary 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: `selection`

ParentImage|endswith: '\appvlp.exe'

Stage 2: `not 1 of filter_main_generic`

or:
Image|endswith: ':\Windows\SysWOW64\rundll32.exe'
Image|endswith: ':\Windows\System32\rundll32.exe'

Stage 3: `not 1 of filter_optional_*`

or:
Image|endswith: '\MSOUC.EXE'
Image|contains: ':\Program Files\Microsoft Office'
Image|endswith: '\SKYPESERVER.EXE'
Image|contains: ':\Program Files\Microsoft Office'
Image|contains: '\SkypeSrv\'
Image|endswith: '\msoasb.exe'
Image|contains: ':\Program Files\Microsoft Office'

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
`Image`	ends_with	`:\Windows\SysWOW64\rundll32.exe` `:\Windows\System32\rundll32.exe` `\MSOUC.EXE` `\SKYPESERVER.EXE` `\msoasb.exe`
`Image`	match	`:\Program Files\Microsoft Office` `\SkypeSrv\`
`ParentImage`	ends_with	`\appvlp.exe`