WARNING THIS IS A EXPERIMENTAL object

We have not been able to test, simulate, or build datasets for this object. Use at your own risk. This analytic is NOT supported.

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Description

This search looks for commands that the SNICat tool uses in the TLS SNI field.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2020-10-21
  • Author: Shannon Davis, Splunk
  • ID: 82d06410-134c-11eb-adc1-0242ac120002

Annotations

ATT&CK
ID Technique Tactic
T1041 Exfiltration Over C2 Channel Exfiltration
Kill Chain Phase
  • Actions on Objectives
NIST
  • PR.DS
  • DE.CM
  • DE.AE
CIS20
  • CIS 13
CVE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
`zeek_ssl` 
| rex field=server_name "(?<snicat>(LIST
|LS
|SIZE
|LD
|CB
|CD
|EX
|ALIVE
|EXIT
|WHERE
|finito)-[A-Za-z0-9]{16}\.)" 
| stats count by src_ip dest_ip server_name snicat 
| where count>0 
| table src_ip dest_ip server_name snicat 
| `detect_snicat_sni_exfiltration_filter`

Macros

The SPL above uses the following Macros:

Note that detect_snicat_sni_exfiltration_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • server_name
  • src_ip
  • dest_ip

How To Implement

You must be ingesting Zeek SSL data into Splunk. Zeek data should also be getting ingested in JSON format. We are detecting when any of the predefined SNICat commands are found within the server_name (SNI) field. These commands are LIST, LS, SIZE, LD, CB, EX, ALIVE, EXIT, WHERE, and finito. You can go further once this has been detected, and run other searches to decode the SNI data to prove or disprove if any data exfiltration has taken place.

Known False Positives

Unknown

Associated Analytic story

RBA

Risk Score Impact Confidence Message
25.0 50 50 tbd

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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