16/10/2026
Fortinet's newly disclosed CVE-2025-61624 is a reminder that the most dangerous cyberattacks are often the hardest to see. After gaining privileged access, attackers used the vulnerability to deploy PEERSTITCH, a sophisticated malware implant that embeds itself within trusted FortiOS processes and selectively bypasses VPN security checks. Unlike traditional malware, it leaves the firewall appearing fully operational while quietly undermining the controls designed to protect the network. The result is a troubling scenario where organisations may believe they are secure, even as attackers evade detection and maintain persistent access. This incident reinforces a critical reality: when trust in security infrastructure is compromised, the firewall can become part of the attack surface rather than the defence.
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PEERSTITCH alters trusted FortiOS processes to bypass checks on selected VPN sessions. Its deployment exposes the real risks of compromised firewall management.