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Detection rules › Sigma

WebDav Client Execution Via Rundll32.EXE

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research)
Source
github.com/SigmaHQ/sigma

Detects "svchost.exe" spawning "rundll32.exe" with command arguments like "C:\windows\system32\davclnt.dll,DavSetCookie". This could be an indicator of exfiltration or use of WebDav to launch code (hosted on a WebDav server).

MITRE ATT&CK coverage

TacticTechniques
ExfiltrationT1048.003 Exfiltration Over Alternative Protocol: Exfiltration Over Unencrypted Non-C2 Protocol

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: WebDav Client Execution Via Rundll32.EXE
id: 2dbd9d3d-9e27-42a8-b8df-f13825c6c3d5
status: test
description: |
    Detects "svchost.exe" spawning "rundll32.exe" with command arguments like "C:\windows\system32\davclnt.dll,DavSetCookie".
    This could be an indicator of exfiltration or use of WebDav to launch code (hosted on a WebDav server).
references:
    - https://github.com/OTRF/detection-hackathon-apt29/issues/17
    - https://github.com/OTRF/ThreatHunter-Playbook/blob/2d4257f630f4c9770f78d0c1df059f891ffc3fec/docs/evals/apt29/detections/7.B.4_C10730EA-6345-4934-AA0F-B0EFCA0C4BA6.md
author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research)
date: 2020-05-02
modified: 2023-09-18
tags:
    - attack.exfiltration
    - attack.t1048.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\svchost.exe'
    selection_img:
        - Image|endswith: '\rundll32.exe'
        - OriginalFileName: 'RUNDLL32.EXE'
    selection_cli:
        CommandLine|contains: 'C:\windows\system32\davclnt.dll,DavSetCookie'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_parent

selection_parent:
    ParentImage|endswith: '\svchost.exe'

Stage 2: selection_img

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

Stage 3: selection_cli

selection_cli:
    CommandLine|contains: 'C:\windows\system32\davclnt.dll,DavSetCookie'

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
  • C:\windows\system32\davclnt.dll,DavSetCookie corpus 3 (sigma 3)
Imageends_with
  • \rundll32.exe corpus 95 (sigma 95)
OriginalFileNameeq
  • RUNDLL32.EXE corpus 62 (sigma 35, splunk 21, elastic 6)
ParentImageends_with
  • \svchost.exe corpus 14 (sigma 14)