File Download Via InstallUtil.EXE

Severity: medium
Author: Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects use of .NET InstallUtil.exe in order to download arbitrary files. The files will be written to "%LOCALAPPDATA%\Microsoft\Windows\INetCache\IE"

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218` System Binary Proxy Execution

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\InstallUtil.exe'
OriginalFileName: InstallUtil.exe

Stage 2: `all of selection_cli`

or:
CommandLine|contains: 'ftp://'
CommandLine|contains: 'http://'
CommandLine|contains: 'https://'

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
`CommandLine`	match	`ftp://` corpus 7 (sigma 7) `http://` corpus 15 (sigma 15) `https://` corpus 14 (sigma 14)
`Image`	ends_with	`\InstallUtil.exe` corpus 5 (sigma 5)
`OriginalFileName`	eq	`InstallUtil.exe` corpus 5 (sigma 5)