Rundll32 Execution Without CommandLine Parameters

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

Detects suspicious start of rundll32.exe without any parameters as found in CobaltStrike beacon activity

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1202` Indirect Command Execution

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `selection`

or:
CommandLine|endswith: '\rundll32'
CommandLine|endswith: '\rundll32.exe'
CommandLine|endswith: '\rundll32.exe"'

Stage 2: `not filter`

or:
ParentImage|contains: '\AppData\Local\'
ParentImage|contains: '\Microsoft\Edge\'

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	`\rundll32` `\rundll32.exe` corpus 2 (sigma 2) `\rundll32.exe"`
`ParentImage`	match	`\AppData\Local\` corpus 3 (sigma 3) `\Microsoft\Edge\`