Outbound Network Connection Initiated By Microsoft Dialer

Hunt Hypothesis

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 Win

Detection Rule

Sigma (Original)

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    This is an outdated process in the current conext of it's usage and is a common target for info stealers for process injection, and is used to make C2 connections, common example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

KQL (Azure Sentinel)

imNetworkSession
| where ((SrcProcessName endswith ":\\Windows\\System32\\dialer.exe" or DstProcessName endswith ":\\Windows\\System32\\dialer.exe") and NetworkDirection =~ "true") and (not((ipv4_is_in_range(DstIpAddr, "127.0.0.0/8") or ipv4_is_in_range(DstIpAddr, "10.0.0.0/8") or ipv4_is_in_range(DstIpAddr, "172.16.0.0/12") or ipv4_is_in_range(DstIpAddr, "192.168.0.0/16") or ipv4_is_in_range(DstIpAddr, "169.254.0.0/16") or ipv4_is_in_range(DstIpAddr, "::1/128") or ipv4_is_in_range(DstIpAddr, "fe80::/10") or ipv4_is_in_range(DstIpAddr, "fc00::/7"))))

Required Data Sources

Sentinel Table	Notes
`imNetworkSession`	Ensure this data connector is enabled

False Positive Guidance

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.

MITRE ATT&CK Context

Tactic: Execution
Tactic: Command and Control
Technique: T1071.001 — T1071.001