ISO or Image Mount Indicator in Recent Files

Severity: medium
Author: Florian Roth (Nextron Systems)
Source: upstream

Detects the creation of recent element file that points to an .ISO, .IMG, .VHD or .VHDX file as often used in phishing attacks. This can be a false positive on server systems but on workstations users should rarely mount .iso or .img files.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566.001` Phishing: Spearphishing Attachment

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

or:
TargetFilename|endswith: .img.lnk
TargetFilename|endswith: .iso.lnk
TargetFilename|endswith: .vhd.lnk
TargetFilename|endswith: .vhdx.lnk
TargetFilename|contains: '\Microsoft\Windows\Recent\'

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.