Outbound Network Connection To Public IP Via Winlogon

Hunt Hypothesis

Detects a “winlogon.exe” process that initiate network communications with public IP addresses

Detection Rule

Sigma (Original)

title: Outbound Network Connection To Public IP Via Winlogon
id: 7610a4ea-c06d-495f-a2ac-0a696abcfd3b
status: test
description: Detects a "winlogon.exe" process that initiate network communications with public IP addresses
references:
    - https://www.microsoft.com/en-us/security/blog/2023/04/11/guidance-for-investigating-attacks-using-cve-2022-21894-the-blacklotus-campaign/
author: Christopher Peacock @securepeacock, SCYTHE @scythe_io
date: 2023-04-28
modified: 2024-03-12
tags:
    - attack.execution
    - attack.command-and-control
    - attack.stealth
    - attack.t1218.011
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        Image|endswith: '\winlogon.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:
    - Communication to other corporate systems that use IP addresses from public address spaces
level: medium

KQL (Azure Sentinel)

imNetworkSession
| where ((SrcProcessName endswith "\\winlogon.exe" or DstProcessName endswith "\\winlogon.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

False Positive Guidance

• Communication to other corporate systems that use IP addresses from public address spaces

MITRE ATT&CK Context

• Tactic: Execution
• Tactic: Command and Control
• Technique: T1218.011 — T1218.011

References

• https://www.microsoft.com/en-us/security/blog/2023/04/11/guidance-for-investigating-attacks-using-cve-2022-21894-the-blacklotus-campaign/
• SigmaHQ Rule