: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 attempts to exploit the Zerologon CVE-2020-1472 vulnerability through Zeek RPC. By detecting attempts to exploit the Zerologon vulnerability through Zeek RPC, SOC analysts can identify potential threats earlier and take appropriate action to mitigate the risks. This detection is made by a Splunk query that looks for specific Zeek RPC operations, including NetrServerPasswordSet2, NetrServerReqChallenge, and NetrServerAuthenticate3, which are aggregated by source and destination IP address and time. This detection is important because it suggests that an attacker is attempting to exploit the Zerologon vulnerability to gain unauthorized access to the domain controller. Zerologon vulnerability is a critical vulnerability that allows attackers to take over domain controllers without authentication, leading to a complete takeover of an organization's IT infrastructure. The impact of such an attack can be severe, potentially leading to data theft, ransomware, or other devastating outcomes. False positives might occur since legitimate Zeek RPC activity can trigger the analytic. Next steps include reviewing the identified source and destination IP addresses and the specific RPC operations used. Capture and inspect any relevant on-disk artifacts, and review concurrent processes to identify the attack source upon triage .

  • Type: TTP

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

  • Last Updated: 2020-09-15
  • Author: Shannon Davis, Splunk
  • ID: bf7a06ec-f703-11ea-adc1-0242ac120002

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1190 Exploit Public-Facing Application Initial Access
Kill Chain Phase
  • Delivery
NIST
  • DE.CM
CIS20
  • CIS 13
CVE
ID Summary CVSS
CVE-2020-1472 An elevation of privilege vulnerability exists when an attacker establishes a vulnerable Netlogon secure channel connection to a domain controller, using the Netlogon Remote Protocol (MS-NRPC), aka 'Netlogon Elevation of Privilege Vulnerability'. 9.3 


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`zeek_rpc` operation IN (NetrServerPasswordSet2,NetrServerReqChallenge,NetrServerAuthenticate3) 
| bin span=5m _time 
| stats values(operation) dc(operation) as opscount count(eval(operation=="NetrServerReqChallenge")) as challenge count(eval(operation=="NetrServerAuthenticate3")) as authcount count(eval(operation=="NetrServerPasswordSet2")) as passcount count as totalcount by _time,src_ip,dest_ip 
| search opscount=3 authcount>4 passcount>0 
| search `detect_zerologon_via_zeek_filter`

Macros

The SPL above uses the following Macros:

:information_source: detect_zerologon_via_zeek_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
  • operation

How To Implement

You must be ingesting Zeek DCE-RPC data into Splunk. Zeek data should also be getting ingested in JSON format. We are detecting when all three RPC operations (NetrServerReqChallenge, NetrServerAuthenticate3, NetrServerPasswordSet2) are splunk_security_essentials_app via bro:rpc:json. These three operations are then correlated on the Zeek UID field.

Known False Positives

unknown

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