VHD Image Download Via Browser

Severity: medium
Author: frack113, Christopher Peacock '@securepeacock', SCYTHE '@scythe_io'
Source: upstream

Detects creation of ".vhd"/".vhdx" files by browser processes. Malware can use mountable Virtual Hard Disk ".vhd" files to encapsulate payloads and evade security controls.

MITRE ATT&CK coverage

Tactic	Techniques
Resource Development	`T1587.001` Develop Capabilities: Malware

Event coverage

Provider	Event ID	Title
Sysmon	11	FileCreate

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\MicrosoftEdge.exe'
Image|endswith: '\brave.exe'
Image|endswith: '\chrome.exe'
Image|endswith: '\firefox.exe'
Image|endswith: '\iexplore.exe'
Image|endswith: '\maxthon.exe'
Image|endswith: '\msedge.exe'
Image|endswith: '\msedgewebview2.exe'
Image|endswith: '\opera.exe'
Image|endswith: '\safari.exe'
Image|endswith: '\seamonkey.exe'
Image|endswith: '\vivaldi.exe'
Image|endswith: '\whale.exe'
TargetFilename|contains: .vhd

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.