DNS Exfiltration Using Nslookup App

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Description

This search is to detect potential DNS exfiltration using nslookup application. This technique are seen in couple of malware and APT group to exfiltrated collected data in a infected machine or infected network. This detection is looking for unique use of nslookup where it tries to use specific record type, TXT, A, AAAA, that are commonly used by attacker and also the retry parameter which is designed to query C2 DNS multiple tries.

• Type: TTP

• Product: Splunk Behavioral Analytics

• Last Updated: 2021-12-07
• Author: Michael Haag, Splunk
• ID: 2452e632-9e0d-11eb-34ba-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1048	Exfiltration Over Alternative Protocol	Exfiltration

Kill Chain Phase

• Actions On Objectives

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

 $main = from source  
| eval timestamp = time  
| eval metadata_uid = metadata.uid  
| eval process_pid = process.pid 
| eval process_file = process.file 
| eval process_file_path = process_file.path 
| eval process_file_name = lower(process_file.name) 
| eval process_cmd_line = process.cmd_line 
| eval actor_user = actor.user 
| eval actor_user_name = actor_user.name 
| eval actor_process = actor.process 
| eval actor_process_pid = actor_process.pid 
| eval actor_process_file = actor_process.file 
| eval actor_process_file_path = actor_process_file.path 
| eval actor_process_file_name = actor_process_file.name 
| eval device_hostname = device.hostname 
| where (process_cmd_line LIKE "%-retry=%" OR process_cmd_line LIKE "%-type=%" OR process_cmd_line LIKE "%-q=%" OR process_cmd_line LIKE "%-qt=%" OR process_cmd_line LIKE "%-querytype=%") AND process_file_name="nslookup.exe" --finding_report--

Macros

The SPL above uses the following Macros:

dns_exfiltration_using_nslookup_app_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.

• process.pid
• process.file.path
• process.file.name
• process.cmd_line
• actor.user.name
• actor.process.pid
• actor.process.file.path
• actor.process.file.name
• device.hostname

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint_Processess datamodel.

Known False Positives

It is possible for some legitimate administrative utilities to use similar process parameters. Filter as needed.

Associated Analytic Story

• Suspicious DNS Traffic
• Dynamic DNS
• Data Exfiltration
• Command And Control

RBA

Risk Score	Impact	Confidence	Message
72.0	90	80	An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest_device_id$ by user $dest_user_id$ performing activity related to DNS exfiltration.

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

• https://www.mandiant.com/resources/fin7-spear-phishing-campaign-targets-personnel-involved-sec-filings
• https://www.varonis.com/blog/dns-tunneling
• https://www.microsoft.com/security/blog/2021/01/20/deep-dive-into-the-solorigate-second-stage-activation-from-sunburst-to-teardrop-and-raindrop/

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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