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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: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-04-21
  • Author: Teoderick Contreras, Stanislav Miskovic, Splunk
  • ID: 0a69fdaa-a2b8-11eb-b16d-acde48001122

ATT&CK

ID Technique Tactic
T1048 Exfiltration Over Alternative Protocol Exfiltration
`sysmon` EventCode = 1 process_name = "nslookup.exe" 
|  bucket _time span=15m 
| stats count as numNsLookup by Computer, _time 
|  eventstats avg(numNsLookup) as avgNsLookup, stdev(numNsLookup) as stdNsLookup, count as numSlots by Computer 
|  eval upperThreshold=(avgNsLookup + stdNsLookup *3) 
|  eval isOutlier=if(avgNsLookup > 20 and avgNsLookup >= upperThreshold, 1, 0) 
|  search isOutlier=1 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `excessive_usage_of_nslookup_app_filter`

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances of nslookup.exe may be used.

Required field

  • _time
  • Computer
  • process_name
  • EventCode

Kill Chain Phase

  • Exploitation

Known False Positives

unknown

RBA

Risk Score Impact Confidence Message
28.0 40 70 Excessive usage of nslookup.exe has been detected on $Computer$. This detection is triggered as as it violates the dynamic threshold

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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