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Description

This search is designed to detect high frequency of archive files data exfiltration through HTTP POST method protocol. This are one of the common techniques used by APT or trojan spy after doing the data collection like screenshot, recording, sensitive data to the infected machines. The attacker may execute archiving command to the collected data, save it a temp folder with a hidden attribute then send it to its C2 through HTTP POST. Sometimes adversaries will rename the archive files or encode/encrypt to cover their tracks. This detection can detect a renamed archive files transfer to HTTP POST since it checks the request body header. Unfortunately this detection cannot support archive that was encrypted or encoded before doing the exfiltration.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Network_Traffic
  • Last Updated: 2021-04-21
  • Author: Teoderick Contreras, Splunk
  • ID: 4477f3ea-a28f-11eb-b762-acde48001122

ATT&CK

ID Technique Tactic
T1048.003 Exfiltration Over Unencrypted/Obfuscated Non-C2 Protocol Exfiltration
`stream_http` http_method=POST 
|eval archive_hdr1=substr(form_data,1,2) 
| eval archive_hdr2 = substr(form_data,1,4) 
|stats values(form_data) as http_request_body min(_time) as firstTime max(_time) as lastTime count by http_method http_user_agent uri_path url bytes_in bytes_out archive_hdr1 archive_hdr2 
|where count >20 AND (archive_hdr1 = "7z" OR archive_hdr1 = "PK" OR archive_hdr2="Rar!") 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `multiple_archive_files_http_post_traffic_filter`

Associated Analytic Story

How To Implement

To successfully implement this search, you need to be ingesting logs with the stream HTTP logs or network logs that catch network traffic. Make sure that the http-request-body, payload, or request field is enabled in stream http configuration.

Required field

  • _time
  • http_method
  • http_user_agent
  • uri_path
  • url
  • bytes_in
  • bytes_out
  • archive_hdr1
  • archive_hdr2
  • form_data

Kill Chain Phase

  • Exfiltration

Known False Positives

Normal archive transfer via HTTP protocol may trip this detection.

RBA

Risk Score Impact Confidence Message
25.0 50 50 A http post $http_method$ sending packet with possible archive bytes header 4form_data$ in uri path $uri_path$

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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