ID | Technique | Tactic |
---|---|---|
T1048 | Exfiltration Over Alternative Protocol | Exfiltration |
Detection: Excessive Usage of NSLOOKUP App
Description
The following analytic detects excessive usage of the nslookup application, which may indicate potential DNS exfiltration attempts. It leverages Sysmon EventCode 1 to monitor process executions, specifically focusing on nslookup.exe. The detection identifies outliers by comparing the frequency of nslookup executions against a calculated threshold. This activity is significant as it can reveal attempts by malware or APT groups to exfiltrate data via DNS queries. If confirmed malicious, this behavior could allow attackers to stealthily transfer sensitive information out of the network, bypassing traditional data exfiltration defenses.
Search
1`sysmon` EventCode = 1 process_name = "nslookup.exe"
2| bucket _time span=1m
3| stats count as numNsLookup by dest, _time
4| eventstats avg(numNsLookup) as avgNsLookup, stdev(numNsLookup) as stdNsLookup, count as numSlots by dest
5| eval upperThreshold=(avgNsLookup + stdNsLookup *3)
6| eval isOutlier=if(numNsLookup > 20 and numNsLookup >= upperThreshold, 1, 0)
7| search isOutlier=1
8| `security_content_ctime(firstTime)`
9| `security_content_ctime(lastTime)`
10| `excessive_usage_of_nslookup_app_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
CrowdStrike ProcessRollup2 | N/A | 'crowdstrike:events:sensor' |
'crowdstrike' |
Sysmon EventID 1 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
Windows Event Log Security 4688 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Security' |
Macros Used
Name | Value |
---|---|
security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
excessive_usage_of_nslookup_app_filter | search * |
excessive_usage_of_nslookup_app_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 Risk Event | True |
Implementation
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.
Known False Positives
unknown
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Excessive usage of nslookup.exe has been detected on $dest$. This detection is triggered as as it violates the dynamic threshold | 28 | 40 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
XmlWinEventLog |
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: 4