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Description

The following analytic identifies a suspicious process that deletes the Mark-of-the-Web (MOTW) data stream. It leverages Sysmon EventCode 23 to detect when a file's Zone.Identifier stream is removed. This activity is significant because it is a common technique used by malware, such as Ave Maria RAT, to bypass security restrictions on files downloaded from the internet. If confirmed malicious, this behavior could allow an attacker to execute potentially harmful files without triggering security warnings, leading to further compromise of the system.

  • Type: TTP

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

  • Last Updated: 2024-05-11
  • Author: Teoderick Contreras, Splunk
  • ID: 8ca13343-7405-4916-a2d1-ae34ce0c28ae

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1553.005 Mark-of-the-Web Bypass Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


1
2
3
4
5



`sysmon` EventCode=23 TargetFilename = "*:Zone.Identifier" 
| stats  min(_time) as firstTime max(_time) as lastTime count by user EventCode Image TargetFilename ProcessID dest 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_mark_of_the_web_bypass_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_mark_of_the_web_bypass_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.

  • EventCode
  • TargetFilename
  • dest
  • user
  • Image
  • ProcessID
  • _time

How To Implement

To successfully implement this search, you need to be ingesting logs with the deleted target file name, process name and process id from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
49.0 70 70 A mark-of-the-web data stream is deleted on $dest$

:information_source: 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

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

source | version: 2