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Remote File Copy via TeamViewer

Elastic Stack Serverless Security

Identifies an executable or script file remotely downloaded via a TeamViewer transfer session.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.*
  • 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
  • Command and Control

Version: 7

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

Attackers commonly transfer tooling or malware from external systems into a compromised environment using the command
and control channel. However, they can also abuse legitimate utilities to drop these files.

TeamViewer is a remote access and remote control tool used by helpdesks and system administrators to perform various
support activities. It is also frequently used by attackers and scammers to deploy malware interactively and other
malicious activities. This rule looks for the TeamViewer process creating files with suspicious extensions.

  • 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.
  • Contact the user to gather information about who and why was conducting the remote access.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Check whether the company uses TeamViewer for the support activities and if there is a support ticket related to this
    access.
  • Retrieve the file 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 tasks 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 mechanism can be used legitimately. Analysts can dismiss the alert if the company relies on TeamViewer to conduct
    remote access and the triage has not identified suspicious or malicious files.
  • 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.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and
    malware components.
  • 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.
  • 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).

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate event.ingested to @timestamp for this rule to work.

Rule query

file where event.type == "creation" and process.name : "TeamViewer.exe" and
  file.extension : ("exe", "dll", "scr", "com", "bat", "ps1", "vbs", "vbe", "js", "wsh", "hta")

Framework: MITRE ATT&CKTM