Desktop.INI Created by Uncommon Process

Severity: medium
Author: Maxime Thiebaut (@0xThiebaut), Tim Shelton (HAWK.IO)
Source: upstream

Detects unusual processes accessing desktop.ini, which can be leveraged to alter how Explorer displays a folder's content (i.e. renaming files) without changing them on disk.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1547.009` Boot or Logon Autostart Execution: Shortcut Modification
Privilege Escalation	`T1547.009` Boot or Logon Autostart Execution: Shortcut Modification

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

TargetFilename|endswith: '\desktop.ini'

Stage 2: `not 1 of filter_main_*`

or:
Image|startswith: 'C:\Program Files (x86)\'
Image|startswith: 'C:\Program Files\'
Image|startswith: 'C:\Windows\'
TargetFilename|startswith: 'C:\$WINDOWS.~BT\NewOS\'

Stage 3: `not 1 of filter_optional_*`

or:
Image|endswith: '\AppData\Local\JetBrains\Toolbox\bin\7z.exe'
Image|startswith: 'C:\Users\'
TargetFilename|contains: '\JetBrains\apps\'
Image|contains: '\AppData\Local\Microsoft\OneDrive\'
Image|startswith: 'C:\Users\'

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	`\AppData\Local\JetBrains\Toolbox\bin\7z.exe`
`Image`	match	`\AppData\Local\Microsoft\OneDrive\` corpus 4 (sigma 4)
`Image`	starts_with	`C:\Program Files (x86)\` corpus 14 (sigma 14) `C:\Program Files\` corpus 15 (sigma 15) `C:\Users\` corpus 7 (sigma 7) `C:\Windows\` corpus 4 (sigma 4)
`TargetFilename`	ends_with	`\desktop.ini`
`TargetFilename`	match	`\JetBrains\apps\`
`TargetFilename`	starts_with	`C:\$WINDOWS.~BT\NewOS\` corpus 2 (sigma 2)