RegAsm.EXE Initiating Network Connection To Public IP — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: medium. Source dates: 2024-04-25 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: b14d03605e62155b97fa7e36ca22ab8e97c86637e8063d00bac65cf0f4d2e875

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: RegAsm.EXE Initiating Network Connection To Public IP
id: 0531e43a-d77d-47c2-b89f-5fe50321c805
status: test
description: Detects "RegAsm.exe" initiating a network connection to public IP adresses
references:
    - https://app.any.run/tasks/ec207948-4916-47eb-a0f4-4c6abb2e7668/
    - https://research.splunk.com/endpoint/07921114-6db4-4e2e-ae58-3ea8a52ae93f/
    - https://lolbas-project.github.io/lolbas/Binaries/Regasm/
author: frack113
date: 2024-04-25
tags:
    - attack.stealth
    - attack.t1218.009
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Initiated: 'true'
        Image|endswith: '\regasm.exe'
    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:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://app.any.run/tasks/ec207948-4916-47eb-a0f4-4c6abb2e7668/
• https://research.splunk.com/endpoint/07921114-6db4-4e2e-ae58-3ea8a52ae93f/
• https://lolbas-project.github.io/lolbas/Binaries/Regasm/