LOLBIN Execution From Abnormal Drive

Severity: medium
Author: Christopher Peacock '@securepeacock', SCYTHE '@scythe_io', Angelo Violetti - SEC Consult '@angelo_violetti', Aaron Herman
Source: upstream

Detects LOLBINs executing from an abnormal or uncommon drive such as a mounted ISO.

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\calc.exe'
Image|endswith: '\certutil.exe'
Image|endswith: '\cmstp.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\installutil.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Image|endswith: '\wscript.exe'
OriginalFileName: CALC.EXE
OriginalFileName: CMSTP.EXE
OriginalFileName: CertUtil.exe
OriginalFileName: MSHTA.EXE
OriginalFileName: REGSVR32.EXE
OriginalFileName: RUNDLL32.EXE
OriginalFileName: cscript.exe
OriginalFileName: installutil.exe
OriginalFileName: wscript.exe

Stage 2: `not 1 of filter_main_*`

or:
CurrentDirectory: ''
CurrentDirectory: null
CurrentDirectory|contains: 'C:\'

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
`CurrentDirectory`	match	`C:\`
`Image`	ends_with	`\calc.exe` corpus 13 (sigma 13) `\certutil.exe` corpus 34 (sigma 34) `\cmstp.exe` corpus 9 (sigma 9) `\cscript.exe` corpus 64 (sigma 64) `\installutil.exe` corpus 5 (sigma 5) `\mshta.exe` corpus 57 (sigma 57) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76) `\wscript.exe` corpus 64 (sigma 64)
`OriginalFileName`	eq	`CALC.EXE` `CMSTP.EXE` corpus 4 (sigma 4) `CertUtil.exe` corpus 13 (sigma 13) `MSHTA.EXE` corpus 7 (sigma 7) `REGSVR32.EXE` corpus 10 (sigma 10) `RUNDLL32.EXE` corpus 28 (sigma 25, splunk 3) `cscript.exe` corpus 15 (sigma 15) `installutil.exe` `wscript.exe` corpus 15 (sigma 15)