Detection: Detect Windows DNS SIGRed via Zeek

EXPERIMENTAL DETECTION

This detection status is set to experimental. The Splunk Threat Research team has not yet fully tested, simulated, or built comprehensive datasets for this detection. As such, this analytic is not officially supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2026-01-14 ID: c5c622e4-d073-11ea-87d0-0242ac130003 Author: Shannon Davis, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the presence of SIGRed, a critical DNS vulnerability, using Zeek DNS and Zeek Conn data. It identifies specific DNS query types (SIG and KEY) and checks for high data transfer within a flow. This detection is significant because SIGRed allows attackers to execute remote code on Windows DNS servers, potentially leading to unauthorized access and control. If confirmed malicious, this activity could result in data exfiltration, service disruption, or further network compromise. Immediate investigation and mitigation, such as patching or isolating the affected server, are crucial.

Search

 1
 2| tstats `security_content_summariesonly` count from datamodel=Network_Resolution where 
 3  DNS.query_type IN (SIG,KEY) by DNS.flow_id
 4
 5| rename DNS.flow_id as flow_id
 6
 7| append [
 8  
 9| tstats  `security_content_summariesonly` count
10  from datamodel=Network_Traffic where
11  All_Traffic.bytes_in>65000
12  by All_Traffic.flow_id
13  
14| rename All_Traffic.flow_id as flow_id
15]
16
17| stats count by flow_id
18
19| where count>1
20
21| fields - count'
22
23| `detect_windows_dns_sigred_via_zeek_filter`

Data Source

No data sources specified for this detection.

Macros Used

Name	Value
security_content_summariesonly	`summariesonly=`summariesonly_config `allow_old_summaries=`oldsummaries_config `fillnull_value=`fillnull_config``
detect_windows_dns_sigred_via_zeek_filter	`search *`

detect_windows_dns_sigred_via_zeek_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1203	Exploitation for Client Execution	Execution

Installation

DE.CM

CIS 10

CVE

CVE-2020-1350

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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

No false positives have been identified at this time.

Associated Analytic Story

Windows DNS SIGRed CVE-2020-1350

Risk Based Analytics (RBA)

Risk Message:

Potential SIGRed activity detected

Risk Object	Risk Object Type	Risk Score	Threat Objects
flow_id	other	25	No Threat Objects

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	❌ Failing	N/A	`N/A`	`N/A`
Integration	❌ Failing	N/A	`N/A`	`N/A`

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: GitHub | Version: 8