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Remotely Started Services via RPC

Elastic Stack Serverless Security

Identifies remote execution of Windows services over remote procedure call (RPC). This could be indicative of lateral movement, but will be noisy if commonly done by administrators."

Rule type: eql

Rule indices:

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

Severity: medium

Risk score: 47

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
  • Lateral Movement
  • Investigation Guide

Version: 102

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

The Service Control Manager Remote Protocol is a client/server protocol used for configuring and controlling service
programs running on a remote computer. A remote service management session begins with the client initiating the
connection request to the server. If the server grants the request, the connection is established. The client can then
make multiple requests to modify, query the configuration, or start and stop services on the server by using the same
session until the session is terminated.

This rule detects the remote creation or start of a service by correlating a services.exe network connection and the
spawn of a child process.

Note:
This investigation guide uses the Osquery Markdown Plugin introduced in Elastic stack version 8.5.0. Older Elastic stacks versions will see unrendered markdown in this guide.

  • Review login events (e.g., 4624) in the alert timeframe to identify the account used to perform this action. Use the
    source.address field to help identify the source system.
  • Review network events from the source system using the source port identified on the alert and try to identify the
    program used to initiate the action.
  • 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.
  • Validate if the activity is not related to planned patches, updates, network administrator activity, or legitimate
    software installations.
  • Examine the host for derived artifacts that indicates 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{"query":"SELECT * FROM dns_cache", "label":"Osquery - Retrieve DNS Cache"}}
      • 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{"query":"SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services","label":"Osquery - Retrieve All Services"}}
        • !{osquery{"query":"SELECT description, display_name, name, path, pid, service_type, start_type, status, user_account FROM services WHERE NOT (user_account LIKE "%LocalSystem" OR user_account LIKE "%LocalService" OR user_account LIKE "%NetworkService" OR user_account == null)","label":"Osquery - Retrieve Services Running on User Accounts"}}
        • !{osquery{"query":"SELECT concat('https://www.virustotal.com/gui/file/', sha1) AS VtLink, name, description, start_type, status, pid, services.path FROM services JOIN authenticode ON services.path = authenticode.path OR services.module_path = authenticode.path JOIN hash ON services.path = hash.path WHERE authenticode.result != "trusted"","label":"Osquery - Retrieve Service Unsigned Executables with Virustotal Link"}}
    • 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.
  • Remote management software like SCCM may trigger this rule. If noisy on your environment, consider adding exceptions.
  • Initiate the incident response process based on the outcome of the triage.
  • Isolate the involved hosts 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

sequence with maxspan=1s
   [network where process.name : "services.exe" and
      network.direction : ("incoming", "ingress") and network.transport == "tcp" and
      source.port >= 49152 and destination.port >= 49152 and source.ip != "127.0.0.1" and source.ip != "::1"
   ] by host.id, process.entity_id

   [process where event.type == "start" and process.parent.name : "services.exe" and
       not (process.name : "svchost.exe" and process.args : "tiledatamodelsvc") and
       not (process.name : "msiexec.exe" and process.args : "/V") and
       not process.executable :
               ("?:\\Windows\\ADCR_Agent\\adcrsvc.exe",
                "?:\\Windows\\System32\\VSSVC.exe",
                "?:\\Windows\\servicing\\TrustedInstaller.exe",
                "?:\\Windows\\System32\\svchost.exe",
                "?:\\Program Files (x86)\\*.exe",
                "?:\\Program Files\\*.exe",
                "?:\\Windows\\PSEXESVC.EXE",
                "?:\\Windows\\System32\\sppsvc.exe",
                "?:\\Windows\\System32\\wbem\\WmiApSrv.exe",
                "?:\\WINDOWS\\RemoteAuditService.exe",
                "?:\\Windows\\VeeamVssSupport\\VeeamGuestHelper.exe",
                "?:\\Windows\\VeeamLogShipper\\VeeamLogShipper.exe",
                "?:\\Windows\\CAInvokerService.exe",
                "?:\\Windows\\System32\\upfc.exe",
                "?:\\Windows\\AdminArsenal\\PDQ*.exe",
                "?:\\Windows\\System32\\vds.exe",
                "?:\\Windows\\Veeam\\Backup\\VeeamDeploymentSvc.exe",
                "?:\\Windows\\ProPatches\\Scheduler\\STSchedEx.exe",
                "?:\\Windows\\System32\\certsrv.exe",
                "?:\\Windows\\eset-remote-install-service.exe",
                "?:\\Pella Corporation\\Pella Order Management\\GPAutoSvc.exe",
                "?:\\Pella Corporation\\OSCToGPAutoService\\OSCToGPAutoSvc.exe",
                "?:\\Pella Corporation\\Pella Order Management\\GPAutoSvc.exe",
                "?:\\Windows\\SysWOW64\\NwxExeSvc\\NwxExeSvc.exe",
                "?:\\Windows\\System32\\taskhostex.exe")
   ] by host.id, process.parent.entity_id

Framework: MITRE ATT&CKTM