Defacement via File and Web Content Modification Across Platforms

Technique Detected:  Defacement | T1491

ID: DET0238
Domains: Enterprise
Analytics: AN0662, AN0663, AN0664, AN0665, AN0666
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN0662

Adversary modifies website or application-hosted content via unauthorized file changes or script injections, often by exploiting web servers or CMS access.

Log Sources
Data Component Name Channel
File Modification (DC0061) WinEventLog:Security EventCode=4663
Process Creation (DC0032) WinEventLog:Sysmon EventCode=1
Application Log Content (DC0038) WinEventLog:Application Unexpected web application errors or CMS logs showing modification to index.html, default.aspx, or other public-facing files
Mutable Elements
Field Description
target_filenames Environment-specific naming of defacement-prone files like 'index.html', 'main.css', 'app.js'.
TimeWindow Detection based on rapid sequence of file writes and script injections within short time intervals.

AN0663

Adversary gains shell access or uploads a malicious script to deface hosted web content in Nginx, Apache, or other services.

Log Sources
Data Component Name Channel
File Modification (DC0061) auditd:SYSCALL write
Network Traffic Content (DC0085) apache:access_log Unusual HTTP POST or PUT requests to paths such as '/uploads/', '/admin/', or CMS plugin folders
Process Creation (DC0032) linux:syslog Unauthorized sudo or shell access, especially leading to file changes in /var/www or /srv/http
Mutable Elements
Field Description
UploadPathRegex Regex for CMS-specific upload directories subject to defacement (e.g., wp-content/uploads).
FileExtensionScope Types of files to monitor for defacement (e.g., .html, .php, .jsp).

AN0664

Adversary modifies internal or external site content through manipulated application bundles, hosted content, or web server configs.

Log Sources
Data Component Name Channel
Process Creation (DC0032) macos:unifiedlog Execution of unexpected terminal or web scripts modifying /Library/WebServer/Documents
File Modification (DC0061) macos:unifiedlog File creation or overwrite in common web-hosting folders
Mutable Elements
Field Description
TargetDirectoryPath Web root folders will vary depending on how services are configured on macOS (e.g., /Library/WebServer/Documents).

AN0665

Adversary defaces internal VM-hosted portals or web UIs by modifying static content on datastore-mounted paths.

Log Sources
Data Component Name Channel
File Modification (DC0061) esxi:vmkernel Unauthorized file modifications within datastore volumes via shell access or vCLI
Mutable Elements
Field Description
DatastoreVolumeName Each environment’s VMFS/volume mounts will vary in name and path.

AN0666

Adversary uses compromised instance credentials or web application access to deface content hosted in S3 buckets, Azure Blob Storage, or GCP Buckets.

Log Sources
Data Component Name Channel
File Creation (DC0039) CloudTrail:PutObject PutObject
Cloud Storage Access (DC0025) AWS:CloudTrail GetObject
Mutable Elements
Field Description
BucketNameRegex Patterns of S3 or GCP buckets used for static website hosting may vary by organization.
IAMRoleContext Some uploads may appear benign unless enriched with user/role metadata.