Detection rules › Sigma

Suspicious Rundll32 Activity Invoking Sys File

Severity
high
Author
Florian Roth (Nextron Systems)
Source
upstream

Detects suspicious process related to rundll32 based on command line that includes a *.sys file as seen being used by UNC2452

MITRE ATT&CK coverage

TacticTechniques
Defense EvasionT1218.011 System Binary Proxy Execution: Rundll32

Event coverage

ProviderEvent IDTitle
Sysmon1Process creation
Security-Auditing4688A new process has been created.

Stages and Predicates

Stage 1: all of selection1

CommandLine|contains: rundll32.exe

Stage 2: all of selection2

or:
CommandLine|contains: '.sys '
CommandLine|contains: '.sys,'

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.

FieldKindValues
CommandLinematch
  • .sys
  • .sys,
  • rundll32.exe corpus 4 (sigma 4)

Neighbors

Stricter alternatives (narrower than this rule)

The rules below may be useful if you find the current rule is too noisy / lacks specificity.