Suspicious PHP File Written to FreePBX Custom Firmware Directory (via file_event)

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.003Web Shell
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects creation of a PHP file inside the FreePBX tftpboot custom firmware directory. The CVE-2025-57819 file upload flaw drops PHP webshells to this path which normally holds only firmware binaries. A PHP file in this location indicates webshell deployment.

Reporting behind it

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Suspicious PHP File Written to FreePBX Custom Firmware Directory (via file_event)

Pivot detection · T1505.003 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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