Registry Modification to Hidden File Extension

Severity: medium
Author: frack113
Source: upstream

Hides the file extension through modification of the registry

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1137` Office Application Startup

Event coverage

Provider	Event ID	Title
Sysmon	13	RegistryEvent (Value Set)

Stages and Predicates

Stage 1: `1 of selection_HideFileExt`

Details: 'DWORD (0x00000001)'
TargetObject|endswith: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\HideFileExt'

Stage 2: `1 of selection_Hidden`

Details: 'DWORD (0x00000002)'
TargetObject|endswith: '\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Hidden'

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
`Details`	eq	`DWORD (0x00000001)` corpus 37 (sigma 37) `DWORD (0x00000002)` corpus 9 (sigma 9)
`TargetObject`	ends_with	`\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Hidden` `\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\HideFileExt`