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Persistence via Update Orchestrator Service Hijack

Elastic Stack Serverless Security

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

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • logs-windows.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Persistence
  • CVE-2020-1313

Version: 101

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

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.

  • 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.
  • Retrieve the process executable and determine if it is malicious:
    • Use a private sandboxed malware analysis system to perform analysis.
      • Observe and collect information about the following activities:
        • Attempts to contact external domains and addresses.
        • File and registry access, modification, and creation activities.
        • Service creation and launch activities.
        • Scheduled task creation.
    • Use the PowerShell Get-FileHash cmdlet to get the files' SHA-256 hash values.
      • Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
  • 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).

Rule query

process where 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&CKTM