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Persistence via Update Orchestrator Service Hijack

Identifies potential hijacking of the Microsoft Update Orchestrator Service to establish persistence with an integrity level of SYSTEM.

Rule type: eql
Rule indices:

  • endgame-*
  • logs-endpoint.events.process-*
  • logs-m365_defender.event-*
  • logs-sentinel_one_cloud_funnel.*
  • logs-system.security*
  • logs-windows.forwarded*
  • logs-windows.sysmon_operational-*
  • winlogbeat-*

Rule Severity: high
Risk Score: 73
Runs every:
Searches indices from: now-9m
Maximum alerts per execution: ?
References:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Persistence
  • Tactic: Privilege Escalation
  • Use Case: Vulnerability
  • Resources: Investigation Guide
  • Data Source: Elastic Endgame
  • Data Source: Elastic Defend
  • Data Source: Microsoft Defender for Endpoint
  • Data Source: Sysmon
  • Data Source: Windows Security Event Logs
  • Data Source: SentinelOne

Version: ?
Rule authors:

  • Elastic

Rule license: Elastic License v2

Windows Update Orchestrator Service is a DCOM service used by other components to install Windows updates that are already downloaded. Windows Update Orchestrator Service was vulnerable to elevation of privileges (any user to local system) due to an improper authorization of the callers. The vulnerability affected the Windows 10 and Windows Server Core products. Fixed by Microsoft on Patch Tuesday June 2020.

This rule will detect uncommon processes spawned by svchost.exe with UsoSvc as the command line parameters. Attackers can leverage this technique to elevate privileges or maintain persistence.

Note: This investigation guide uses the Osquery Markdown Plugin introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.

  • Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
  • Investigate any abnormal behavior by the subject process such as network connections, registry or file modifications, and any spawned child processes.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Assess whether this behavior is prevalent in the environment by looking for similar occurrences across hosts.
  • Examine the host for derived artifacts that indicate suspicious activities:
    • Analyze the process executable using a private sandboxed analysis system.
    • Observe and collect information about the following activities in both the sandbox and the alert subject host:
      • Attempts to contact external domains and addresses.
        • Use the Elastic Defend network events to determine domains and addresses contacted by the subject process by filtering by the process' process.entity_id.
        • Examine the DNS cache for suspicious or anomalous entries.
          • $osquery_0
      • Use the Elastic Defend registry events to examine registry keys accessed, modified, or created by the related processes in the process tree.
      • Examine the host services for suspicious or anomalous entries.
        • $osquery_1
        • $osquery_2
        • $osquery_3
    • Retrieve the files' SHA-256 hash values using the PowerShell Get-FileHash cmdlet and search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
  • Investigate potentially compromised accounts. Analysts can do this by searching for login events (for example, 4624) to the target host after the registry modification.
  • This activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved host to prevent further post-compromise behavior.
  • If the triage identified malware, search the environment for additional compromised hosts.
    • Implement temporary network rules, procedures, and segmentation to contain the malware.
    • Stop suspicious processes.
    • Immediately block the identified indicators of compromise (IoCs).
    • Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
  • Remove and block malicious artifacts identified during triage.
  • Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
process where host.os.type == "windows" and event.type == "start" and
  process.parent.executable : "C:\\Windows\\System32\\svchost.exe" and
  process.parent.args : "UsoSvc" and
  not process.executable :
          ("?:\\ProgramData\\Microsoft\\Windows\\UUS\\Packages\\*\\amd64\\MoUsoCoreWorker.exe",
          "?:\\Windows\\System32\\UsoClient.exe",
          "?:\\Windows\\System32\\MusNotification.exe",
          "?:\\Windows\\System32\\MusNotificationUx.exe",
          "?:\\Windows\\System32\\MusNotifyIcon.exe",
          "?:\\Windows\\System32\\WerFault.exe",
          "?:\\Windows\\System32\\WerMgr.exe",
          "?:\\Windows\\UUS\\amd64\\MoUsoCoreWorker.exe",
          "?:\\Windows\\System32\\MoUsoCoreWorker.exe",
          "?:\\Windows\\UUS\\amd64\\UsoCoreWorker.exe",
          "?:\\Windows\\System32\\UsoCoreWorker.exe",
          "?:\\Program Files\\Common Files\\microsoft shared\\ClickToRun\\OfficeC2RClient.exe") and
  not process.name : ("MoUsoCoreWorker.exe", "OfficeC2RClient.exe")

Framework: MITRE ATT&CK

Framework: MITRE ATT&CK