CobaltStrike Load by Rundll32

Severity: high
Author: Wojciech Lesicki
Source: upstream

Rundll32 can be use by Cobalt Strike with StartW function to load DLLs from the command line.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218.011` System Binary Proxy Execution: Rundll32

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_rundll`

or:
CommandLine|contains: 'rundll32 '
CommandLine|contains: rundll32.exe
Image|endswith: '\rundll32.exe'
OriginalFileName: RUNDLL32.EXE

Stage 2: `all of selection_params`

or:
CommandLine|endswith: ' StartW'
CommandLine|endswith: ',StartW'
CommandLine|contains: .dll

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`	ends_with	`StartW` `,StartW`
`CommandLine`	match	`.dll` corpus 15 (sigma 15) `rundll32` `rundll32.exe` corpus 4 (sigma 4)
`Image`	ends_with	`\rundll32.exe` corpus 76 (sigma 76)
`OriginalFileName`	eq	`RUNDLL32.EXE` corpus 28 (sigma 25, splunk 3)