Detection rules › Sigma

Rundll32 UNC Path Execution

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Nasreddine Bencherchali (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects rundll32 execution where the DLL is located on a remote location (share)

MITRE ATT&CK coverage

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: Rundll32 UNC Path Execution
id: 5cdb711b-5740-4fb2-ba88-f7945027afac
status: test
description: Detects rundll32 execution where the DLL is located on a remote location (share)
references:
    - https://www.cybereason.com/blog/rundll32-the-infamous-proxy-for-executing-malicious-code
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-10
tags:
    - attack.execution
    - attack.lateral-movement
    - attack.stealth
    - attack.t1021.002
    - attack.t1218.011
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\rundll32.exe'
        - OriginalFileName: 'RUNDLL32.EXE'
        - CommandLine|contains: 'rundll32'
    selection_cli:
        CommandLine|contains: ' \\\\'
    condition: all of selection_*
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_img

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

Stage 2: selection_cli

selection_cli:
    CommandLine|contains: ' \\\\'

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
  • \\\\ corpus 8 (sigma 8)
  • rundll32 corpus 26 (sigma 23, chronicle 2, kusto 1)
Imageends_with
  • \rundll32.exe corpus 95 (sigma 95)
OriginalFileNameeq
  • RUNDLL32.EXE corpus 62 (sigma 35, splunk 21, elastic 6)