: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 presence of SIGRed, a critical DNS vulnerability, using Zeek DNS and Zeek Conn data. SIGRed vulnerability allows attackers to run remote code on Windows DNS servers. By detecting SIGRed early, you can prevent further damage and protect the organization's network infrastructure. The detection is made by identifying specific DNS query types (SIG and KEY) in the Zeek DNS data and checks for high data transfer in the Zeek Conn data. If multiple instances of these indicators are found within a flow, it suggests the presence of SIGRed. The detection is important because it indicates a potential compromise of Windows DNS servers that suggests that an attacker might have gained unauthorized access to the DNS server and can run arbitrary code. The impact of this attack can be severe, leading to data exfiltration, unauthorized access, or disruption of critical services. Next steps include investigating the affected flow and taking immediate action to mitigate the vulnerability. This can involve patching the affected DNS server, isolating the server from the network, or conducting a forensic analysis to determine the extent of the compromise.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Network_Resolution, Network_Traffic
  • Last Updated: 2020-07-28
  • Author: Shannon Davis, Splunk
  • ID: c5c622e4-d073-11ea-87d0-0242ac130003

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1203 Exploitation for Client Execution Execution
Kill Chain Phase
  • Installation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE
ID Summary CVSS
CVE-2020-1350 A remote code execution vulnerability exists in Windows Domain Name System servers when they fail to properly handle requests, aka 'Windows DNS Server Remote Code Execution Vulnerability'. 10.0 


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| tstats `security_content_summariesonly` count from datamodel=Network_Resolution where DNS.query_type IN (SIG,KEY) by DNS.flow_id 
| rename DNS.flow_id as flow_id 
| append [
| tstats  `security_content_summariesonly` count from datamodel=Network_Traffic where All_Traffic.bytes_in>65000 by All_Traffic.flow_id 
| rename All_Traffic.flow_id as flow_id] 
| `detect_windows_dns_sigred_via_zeek_filter` 
| stats count by flow_id 
| where count>1 
| fields - count

Macros

The SPL above uses the following Macros:

:information_source: detect_windows_dns_sigred_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
  • DNS.query_type
  • DNS.flow_id
  • All_Traffic.bytes_in
  • All_Traffic.flow_id

How To Implement

You must be ingesting Zeek DNS and Zeek Conn data into Splunk. Zeek data should also be getting ingested in JSON format. We are detecting SIG and KEY records via bro:dns:json and TCP payload over 65KB in size via bro:conn:json. The Network Resolution and Network Traffic datamodels are in use for this search.

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

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