Elastic
Start free trial
Loading

Conhost Spawned By Suspicious Parent Process

Elastic Stack Serverless Security

Detects when the Console Window Host (conhost.exe) process is spawned by a suspicious parent process, which could be indicative of code injection.

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
  • Execution

Version: 8

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

The Windows Console Host, or conhost.exe, is both the server application for all of the Windows Console APIs as well as
the classic Windows user interface for working with command-line applications.

Attackers often rely on custom shell implementations to avoid using built-in command interpreters like cmd.exe and
PowerShell.exe and bypass application allowlisting and security features. Attackers commonly inject these implementations into
legitimate system processes.

  • 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 abnormal behaviors observed 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.
  • Inspect the host for suspicious or abnormal behaviors in the alert timeframe.
  • Retrieve the parent 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 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 activity is unlikely to happen legitimately. Benign true positives (B-TPs) can be added as exceptions if necessary.
  • Suspicious Process from Conhost - 28896382-7d4f-4d50-9b72-67091901fd26
  • Suspicious PowerShell Engine ImageLoad - 852c1f19-68e8-43a6-9dce-340771fe1be3
  • 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

process where event.type in ("start", "process_started") and
  process.name : "conhost.exe" and
  process.parent.name : ("svchost.exe", "lsass.exe", "services.exe", "smss.exe", "winlogon.exe", "explorer.exe",
                         "dllhost.exe", "rundll32.exe", "regsvr32.exe", "userinit.exe", "wininit.exe", "spoolsv.exe",
                         "wermgr.exe", "csrss.exe", "ctfmon.exe")

Framework: MITRE ATT&CKTM