Outbound Network Connection Initiated By Microsoft Dialer — Sigma Rule

Rule metadata and linked tags

Author: CertainlyP. Source status: test; severity: high. Source dates: 2024-04-26 / not supplied.

{
  "category": "network_connection",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 9c13969b70c3bb98c5b6d722d491df90053e5eb685957bcc183b68e48d243f8f

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Outbound Network Connection Initiated By Microsoft Dialer
id: 37e4024a-6c80-4d8f-b95d-2e7e94f3a8d1
status: test
description: |
    Detects outbound network connection initiated by Microsoft Dialer.
    The Microsoft Dialer, also known as Phone Dialer, is a built-in utility application included in various versions of the Microsoft Windows operating system. Its primary function is to provide users with a graphical interface for managing phone calls via a modem or a phone line connected to the computer.
    This is an outdated process in the current conext of it's usage and is a common target for info stealers for process injection, and is used to make C2 connections, common example is "Rhadamanthys"
references:
    - https://tria.ge/240301-rk34sagf5x/behavioral2
    - https://app.any.run/tasks/6720b85b-9c53-4a12-b1dc-73052a78477d
    - https://research.checkpoint.com/2023/rhadamanthys-v0-5-0-a-deep-dive-into-the-stealers-components/
    - https://strontic.github.io/xcyclopedia/library/dialer.exe-0B69655F912619756C704A0BF716B61F.html
author: CertainlyP
date: 2024-04-26
tags:
    - attack.execution
    - attack.command-and-control
    - attack.t1071.001
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Image|endswith: ':\Windows\System32\dialer.exe'
        Initiated: 'true'
    filter_main_local_ranges:
        DestinationIp|cidr:
            - '127.0.0.0/8'
            - '10.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - '::1/128'  # IPv6 loopback
            - 'fe80::/10'  # IPv6 link-local addresses
            - 'fc00::/7'  # IPv6 private addresses
    condition: selection and not 1 of filter_main_*
falsepositives:
    - In Modern Windows systems, unable to see legitimate usage of this process, However, if an organization has legitimate purpose for this there can be false positives.
level: high

Original YAML and metadata in JSON

False positives

• In Modern Windows systems, unable to see legitimate usage of this process, However, if an organization has legitimate purpose for this there can be false positives.

Source references

• https://tria.ge/240301-rk34sagf5x/behavioral2
• https://app.any.run/tasks/6720b85b-9c53-4a12-b1dc-73052a78477d
• https://research.checkpoint.com/2023/rhadamanthys-v0-5-0-a-deep-dive-into-the-stealers-components/
• https://strontic.github.io/xcyclopedia/library/dialer.exe-0B69655F912619756C704A0BF716B61F.html