Surge in Brute-Force Attacks on Fortinet SSL VPNs Precedes Focus on FortiManager
August 12, 2025
Threat Intelligence / Enterprise Security
Cybersecurity experts are reporting a significant increase in brute-force traffic directed at Fortinet SSL VPN devices. A coordinated effort, noted by threat intelligence firm GreyNoise, was detected on August 3, 2025, involving over 780 unique IP addresses participating in the attack. In the last 24 hours alone, 56 unique malicious IP addresses have been identified, originating from countries including the United States, Canada, Russia, and the Netherlands.
Targets of this brute-force activity span across the United States, Hong Kong, Brazil, Spain, and Japan. GreyNoise emphasized that the attacks were specifically aimed at their FortiOS profile, indicating a deliberate targeting strategy rather than opportunistic behavior. The firm also reported observing two distinct waves of assaults before and after August 5, with one being a prolonged brute-force attack.