Detection of Credential Harvesting via Web Portal Modification

Technique Detected:  Web Portal Capture | T1056.003

ID: DET0480
Domains: Enterprise
Analytics: AN1320, AN1321, AN1322
Version: 1.0
Created: 21 October 2025
Last Modified: 21 October 2025

Analytics

AN1320

Detects unauthorized modifications to login-facing web server files (e.g., index.php, login.js) typically tied to VPN, SSO, or intranet portals. Correlates suspicious file changes with remote access artifacts or web shell behavior.

Log Sources
Data Component Name Channel
File Modification (DC0061) auditd:SYSCALL write
Network Traffic Content (DC0085) NSM:Flow HTTP Request Logging
Mutable Elements
Field Description
MonitoredFilePaths Target login-related files (e.g., /var/www/html/login.php) for integrity monitoring
TimeWindow Tune detection to correlate file edits and web access within a short duration

AN1321

Detects tampering of IIS-based login pages (e.g., default.aspx, login.aspx) tied to VPN, OWA, or SharePoint via script injection or unexpected editor processes modifying web roots.

Log Sources
Data Component Name Channel
File Creation (DC0039) WinEventLog:Sysmon EventCode=11
Network Traffic Content (DC0085) WinEventLog:iis IIS Logs
Mutable Elements
Field Description
FilePath Define path to monitored IIS web root (e.g., C:\inetpub\wwwroot\login.aspx)
ProcessName Exclude legitimate updates (e.g., msdeploy.exe) and alert on suspicious editors (e.g., notepad.exe, certutil.exe)

AN1322

Detects unauthorized changes to locally hosted login pages on macOS (common in developer VPN environments) and links file edits to cron jobs, background scripts, or SUID binaries.

Log Sources
Data Component Name Channel
File Modification (DC0061) fs:fsusage Filesystem Access Logging
Network Traffic Content (DC0085) macos:unifiedlog subsystem=com.apple.WebKit
Mutable Elements
Field Description
WebRootPath Specify custom web service directories (e.g., /Library/WebServer/Documents/)
AnomalousProcess Alert on web root changes from non-web processes or scripts