Threat Huntmediumtest

Dllhost.EXE Initiated Network Connection To Non-Local IP Address

Detects Dllhost.EXE initiating a network connection to a non-local IP address. Aside from Microsoft own IP range that needs to be excluded. Network communication from Dllhost will depend entirely on the hosted DLL. An initial baseline is recommended before deployment.

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Launch

bartblazeCreated Mon Jul 13Updated Tue Jul 16cfed2f44-16df-4bf3-833a-79405198b277windows

Hunting Hypothesis

Log Source

WindowsNetwork Connection

ProductWindows← raw: windows

CategoryNetwork Connection← raw: network_connection

Events for outbound and inbound network connections including DNS resolution.

Detection Logic

detection:
    selection:
        Image|endswith: '\dllhost.exe'
        Initiated: 'true'
    filter_main_local_ranges:
        DestinationIp|cidr:
            - '::1/128'  # IPv6 loopback
            - '10.0.0.0/8'
            - '127.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - 'fc00::/7'  # IPv6 private addresses
            - 'fe80::/10'  # IPv6 link-local addresses
    filter_main_msrange:
        DestinationIp|cidr:
            - '20.184.0.0/13' # Microsoft Corporation
            - '20.192.0.0/10' # Microsoft Corporation
            - '23.72.0.0/13'  # Akamai International B.V.
            - '51.10.0.0/15'  # Microsoft Corporation
            - '51.103.0.0/16' # Microsoft Corporation
            - '51.104.0.0/15' # Microsoft Corporation
            - '52.224.0.0/11'  # Microsoft Corporation
            - '150.171.0.0/19'  # Microsoft Corporation
            - '204.79.197.0/24' # Microsoft Corporation'
    condition: selection and not 1 of filter_main_*