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