SigmaHQ/rules/windows/network_connection/sysmon_rundll32_net_connections.yml

title: Rundll32 Internet Connection
id: cdc8da7d-c303-42f8-b08c-b4ab47230263
status: experimental
description: Detects a rundll32 that communicates with public IP addresses
references:
    - https://www.hybrid-analysis.com/sample/759fb4c0091a78c5ee035715afe3084686a8493f39014aea72dae36869de9ff6?environmentId=100
author: Florian Roth
date: 2017/11/04
modified: 2020/08/24
tags:
    - attack.defense_evasion
    - attack.t1218.011
    - attack.t1085  # an old one
    - attack.execution
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Image|endswith: '\rundll32.exe'
        Initiated: 'true'
    filter:
        DestinationIp|startswith: 
            - '10.'
            - '192.168.'
            - '172.16.'
            - '172.17.'
            - '172.18.'
            - '172.19.'
            - '172.20.'
            - '172.21.'
            - '172.22.'
            - '172.23.'
            - '172.24.'
            - '172.25.'
            - '172.26.'
            - '172.27.'
            - '172.28.'
            - '172.29.'
            - '172.30.'
            - '172.31.'
            - '127.'
    condition: selection and not filter
falsepositives:
    - Communication to other corporate systems that use IP addresses from public address spaces
level: medium