Detectionmediumtest

Potential Obfuscated Ordinal Call Via Rundll32

Detects execution of "rundll32" with potential obfuscated ordinal calls

Convert In Phoenix Studio

Open this Sigma rule in the converter with the YAML preloaded and ready for backend selection.

Nasreddine Bencherchali (Nextron Systems), Swachchhanda Shrawan Poudel (Nextron Systems)Created Wed May 17Updated Sun Feb 2343fa5350-db63-4b8f-9a01-789a427074e1windows

Log Source

WindowsProcess Creation

ProductWindows← raw: windows

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

detection:
    selection_img:
        - Image|endswith: '\rundll32.exe'
        - OriginalFileName: 'RUNDLL32.EXE'
        - CommandLine|contains: 'rundll32'
    selection_cli:
        CommandLine|contains:
            - '#+'
            - '#-'
            # ordinal can be represented by adding any number of zeros in front ordinal number, for e.g. 000000024
            - '#0'
            # ordinal is 16 bit ordinal, so if you make the number large enough (don't fit in 16 bit space), then it normally wraps around.
            # for e.g ordinal 24 can be also represented by 65560 (65536+24)
            - '#655'
            - '#656'
    condition: all of selection_*