Rundll32 Internet Connection

 1title: Rundll32 Internet Connection
 2id: cdc8da7d-c303-42f8-b08c-b4ab47230263
 3status: test
 4description: Detects a rundll32 that communicates with public IP addresses
 5references:
 6    - https://www.hybrid-analysis.com/sample/759fb4c0091a78c5ee035715afe3084686a8493f39014aea72dae36869de9ff6?environmentId=100
 7author: Florian Roth (Nextron Systems)
 8date: 2017-11-04
 9modified: 2024-03-13
10tags:
11    - attack.defense-evasion
12    - attack.t1218.011
13    - attack.execution
14logsource:
15    category: network_connection
16    product: windows
17detection:
18    selection:
19        Image|endswith: '\rundll32.exe'
20        Initiated: 'true'
21    filter_main_local_ranges:
22        DestinationIp|cidr:
23            - '127.0.0.0/8'
24            - '10.0.0.0/8'
25            - '172.16.0.0/12'
26            - '192.168.0.0/16'
27            - '169.254.0.0/16'
28            - '::1/128'  # IPv6 loopback
29            - 'fe80::/10'  # IPv6 link-local addresses
30            - 'fc00::/7'  # IPv6 private addresses
31    filter_main_ms_ranges:
32        DestinationIp|cidr:
33            - '20.0.0.0/8' # Microsoft range, caused some FPs
34            - '51.103.0.0/16' # Microsoft AS8075 range, caused some FPs
35            - '51.104.0.0/16' # Microsoft AS8075 range, caused some FPs
36            - '51.105.0.0/16' # Microsoft AS8075 range, caused some FPs
37    filter_main_app_sdb:
38        CommandLine|endswith: '\system32\PcaSvc.dll,PcaPatchSdbTask'
39    filter_main_azure_managed:
40        SourceHostname|endswith: '.internal.cloudapp.net'
41    filter_main_svchost_update_processes:
42        # Note: This require "ParentImage" data enrichment.
43        ParentImage: 'C:\Windows\System32\svchost.exe'
44        DestinationPort: 443
45    condition: selection and not 1 of filter_main_*
46falsepositives:
47    - Communication to other corporate systems that use IP addresses from public address spaces
48level: medium