:warning: THIS IS A EXPERIMENTAL DETECTION

This detection has been marked experimental by the Splunk Threat Research team. This means we have not been able to test, simulate, or build datasets for this detection. Use at your own risk. This analytic is NOT supported.

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Description

The following analytic detects the creation of permanent event subscriptions using Windows Management Instrumentation (WMI), which is used by attackers to achieve persistence in a compromised system. By creating a permanent event subscription, an attacker can run malicious scripts or binaries in response to specific system events that enables them to maintain access to the system undetected. The detection is made by using Sysmon EventID 5 data to detect instances where the consumers of these events are not the expected "NTEventLogEventConsumer." The detection is important because it identifies unusual or unexpected subscription creation, which suggests that an attacker is attempting to achieve persistence within the environment and might be executing malicious scripts or binaries in response to specific system events. The impact of such an attack can be severe, potentially leading to data theft, ransomware, or other damaging outcomes. False positives might occur since False positives might occur since WMI event subscriptions can be used for legitimate purposes by system administrators. You must have a thorough understanding of WMI activity within the context of the monitored environment to effectively differentiate between legitimate and malicious activity.Next steps include investigating the associated scripts or binaries and identifying the source of the attack.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2018-10-23
  • Author: Rico Valdez, Splunk
  • ID: 71bfdb13-f200-4c6c-b2c9-a2e07adf437d

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1047 Windows Management Instrumentation Execution
Kill Chain Phase
  • Installation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE
1
2
3
4
5
6
7
8
9
`wmi` EventCode=5861 Binding 
| rex field=Message "Consumer =\s+(?<consumer>[^;
|^$]+)" 
| search consumer!="NTEventLogEventConsumer=\"SCM Event Log Consumer\"" 
| stats count min(_time) as firstTime max(_time) as lastTime by ComputerName, consumer, Message 
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)` 
| rename ComputerName as dest 
| `wmi_permanent_event_subscription_filter`

Macros

The SPL above uses the following Macros:

:information_source: wmi_permanent_event_subscription_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • EventCode
  • Message
  • consumer
  • ComputerName

How To Implement

To successfully implement this search, you must be ingesting the Windows WMI activity logs. This can be done by adding a stanza to inputs.conf on the system generating logs with a title of [WinEventLog://Microsoft-Windows-WMI-Activity/Operational].

Known False Positives

Although unlikely, administrators may use event subscriptions for legitimate purposes.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 tbd

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 1