sigma-rules/rules/windows/defense_evasion_regmod_remotemonologue.toml

[metadata]
creation_date = "2025/04/14"
integration = ["endpoint", "m365_defender", "sentinel_one_cloud_funnel", "windows"]
maturity = "production"
updated_date = "2025/09/18"

[rule]
author = ["Elastic"]
description = """
Identifies attempt to perform session hijack via COM object registry modification by setting the RunAs value to
Interactive User.
"""
from = "now-9m"
index = [
    "logs-endpoint.events.registry-*",
    "endgame-*",
    "logs-m365_defender.event-*",
    "logs-sentinel_one_cloud_funnel.*",
    "logs-windows.sysmon_operational-*",
]
language = "eql"
license = "Elastic License v2"
name = "Potential RemoteMonologue Attack"
note = """## Triage and analysis

### Investigating Potential RemoteMonologue Attack


### Possible investigation steps

- Review the registry event logs to confirm the modification of the RunAs value in the specified registry paths, ensuring the change was not part of a legitimate administrative action.
- Identify the user account and process responsible for the registry modification by examining the event logs for associated user and process information.
- Check for any recent remote authentication attempts or sessions on the affected host to determine if this activity is associated with lateral movement or not.
- Investigate the timeline of the registry change to correlate with any other suspicious activities or alerts on the host, such as the execution of unusual processes or network connections.

### False positive analysis

- Software updates or installations that modify COM settings.
- Automated scripts or management tools that adjust COM configurations.

### Response and remediation

- Immediately isolate the affected system from the network to prevent further unauthorized access or lateral movement by the adversary.
- Modify the registry value back to its secure state, ensuring that "RunAs" value is not set to "Interactive User".
- Conduct a thorough review of recent user activity and system logs to identify any unauthorized access or changes made during the period NLA was disabled.
- Reset passwords for all accounts that have accessed the affected system to mitigate potential credential compromise.
- Escalate the incident to the security operations center (SOC) or incident response team for further investigation and to determine if additional systems are affected.
- Implement enhanced monitoring on the affected system and similar endpoints to detect any further attempts to disable NLA or other suspicious activities.
"""
references = [
    "https://www.ibm.com/think/x-force/remotemonologue-weaponizing-dcom-ntlm-authentication-coercions#1",
    "https://github.com/xforcered/RemoteMonologue",
]
risk_score = 47
rule_id = "c18975f5-676c-4091-b626-81e8938aa2ee"
severity = "medium"
tags = [
    "Domain: Endpoint",
    "OS: Windows",
    "Use Case: Threat Detection",
    "Tactic: Defense Evasion",
    "Data Source: Elastic Defend",
    "Data Source: Elastic Endgame",
    "Data Source: Microsoft Defender for Endpoint",
    "Data Source: SentinelOne",
    "Data Source: Sysmon",
    "Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "eql"

query = '''
registry where host.os.type == "windows" and event.action != "deletion" and
  registry.value == "RunAs" and registry.data.strings : "Interactive User" and

  not 
  (
    (
      process.executable : (
        "C:\\ProgramData\\Microsoft\\Windows Defender\\Platform\\4.*\\MsMpEng.exe",
        "C:\\Program Files\\Windows Defender\\MsMpEng.exe"
      ) and
      registry.path : "*\\SOFTWARE\\Classes\\AppID\\{1111A26D-EF95-4A45-9F55-21E52ADF9887}\\RunAs"
    ) or
    (
      process.executable : (
        "C:\\Program Files\\TeamViewer\\TeamViewer.exe",
        "C:\\Program Files (x86)\\TeamViewer\\TeamViewer.exe"
      ) and
      registry.path : "*\\SOFTWARE\\Classes\\AppID\\{850A928D-5456-4865-BBE5-42635F1EBCA1}\\RunAs"
    ) or
    (
      process.executable : "C:\\Windows\\System32\\svchost.exe" and
      registry.path : "*\\S-1-*Classes\\AppID\\{D3E34B21-9D75-101A-8C3D-00AA001A1652}\\RunAs"
    ) or
    (
      process.executable : "C:\\Windows\\System32\\SecurityHealthService.exe" and
      registry.path : (
        "*\\SOFTWARE\\Classes\\AppID\\{1D278EEF-5C38-4F2A-8C7D-D5C13B662567}\\RunAs",
        "*\\SOFTWARE\\Classes\\AppID\\{7E55A26D-EF95-4A45-9F55-21E52ADF9878}\\RunAs"
      )
    ) or
    (
      process.executable : "C:\\Windows\\System32\\SecurityHealthService.exe" and
      registry.path : (
        "*\\SOFTWARE\\Classes\\AppID\\{1D278EEF-5C38-4F2A-8C7D-D5C13B662567}\\RunAs",
        "*\\SOFTWARE\\Classes\\AppID\\{7E55A26D-EF95-4A45-9F55-21E52ADF9878}\\RunAs"
      )
    ) or
    registry.path : (
      "HKLM\\SOFTWARE\\Microsoft\\Office\\ClickToRun\\VREGISTRY_*",
      "\\REGISTRY\\MACHINE\\SOFTWARE\\Microsoft\\Office\\ClickToRun\\VREGISTRY_*"
    ) or
    (process.executable : "C:\\windows\\System32\\msiexec.exe" and ?user.id : "S-1-5-18")
  )
'''


[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1112"
name = "Modify Registry"
reference = "https://attack.mitre.org/techniques/T1112/"

[[rule.threat.technique]]
id = "T1562"
name = "Impair Defenses"
reference = "https://attack.mitre.org/techniques/T1562/"


[rule.threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"