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Detection rules › Sigma

IcedID Malware Suspicious Single Digit DLL Execution Via Rundll32

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

Detects RunDLL32.exe executing a single digit DLL named "1.dll" with the export function "DllRegisterServer". This behaviour was often seen used by malware and especially IcedID

MITRE ATT&CK coverage

TacticTechniques
StealthT1218.011 System Binary Proxy Execution: Rundll32

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

title: IcedID Malware Suspicious Single Digit DLL Execution Via Rundll32
id: 2bd8e100-5b3b-4b6a-bbb5-b129d3ddddc5
status: test
description: Detects RunDLL32.exe executing a single digit DLL named "1.dll" with the export function "DllRegisterServer". This behaviour was often seen used by malware and especially IcedID
references:
    - https://thedfirreport.com/2023/05/22/icedid-macro-ends-in-nokoyawa-ransomware/
    - https://thedfirreport.com/2023/08/28/html-smuggling-leads-to-domain-wide-ransomware/
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-08-31
tags:
    - attack.stealth
    - attack.t1218.011
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\rundll32.exe'
        CommandLine|endswith:
            - '\1.dll, DllRegisterServer' # In case of full path exec
            - ' 1.dll, DllRegisterServer' # In case of direct exec
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith: '\rundll32.exe'
    CommandLine|endswith:
        - '\1.dll, DllRegisterServer'
        - ' 1.dll, DllRegisterServer'

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
CommandLineends_with
  • 1.dll, DllRegisterServer
  • \1.dll, DllRegisterServer
Imageends_with
  • \rundll32.exe corpus 95 (sigma 95)