A significant spike in brute-force attacks targeting Fortinet SSL VPN devices has been detected by cybersecurity researchers. The coordinated activity, first observed on August 3, 2025, involved a large network of over 780 unique IP addresses. This points to a deliberate and concerted effort to breach these devices, rather than a scattershot approach. The malicious IP addresses, originating from countries like the United States, Canada, Russia, and the Netherlands, have been systematically classified as threats, indicating a globally distributed attack infrastructure. This widespread origin suggests a sophisticated and organized campaign, likely leveraging a botnet or a network of compromised machines to carry out the assault.
Precise Targeting of Fortinet’s Infrastructure
The attacks were not opportunistic but were instead deliberately and precisely aimed at Fortinet’s infrastructure. Threat intelligence firm GreyNoise noted that the initial wave of traffic was specifically targeting their “FortiOS profile,” confirming that the attackers were not just scanning for any vulnerable device but were actively seeking out Fortinet’s SSL VPNs. This level of precision suggests the attackers had prior knowledge of the targeted systems or were using a highly refined scanning technique to identify and attack these specific devices. The focus on SSL VPNs is particularly concerning as they are a critical entry point for remote access to corporate networks, making them a high-value target for malicious actors.
Two Distinct Waves of Attack
GreyNoise identified two distinct assault waves, each with unique characteristics. The first wave, observed before August 5, was a long-running brute-force activity with a single, consistent TCP signature. This suggests a sustained and steady attack effort over time. The second wave, which occurred after August 5, was a sudden and concentrated burst of traffic. This second wave had a different TCP signature and, interestingly, was not hitting the FortiOS profile but was instead consistently targeting FortiManager devices. The shift in targets from FortiOS to FortiManager demonstrates a dynamic and adaptive attack strategy, where the attackers are likely trying different methods to gain a foothold within the Fortinet ecosystem.
Global Impact and Vulnerable Regions
The brute-force activity has targeted a wide range of geographical locations, highlighting the global scale of this cyber threat. Countries impacted include the United States, Hong Kong, Brazil, Spain, and Japan. This diverse list of targets indicates that the attackers are not limited to a single region and are attempting to compromise systems across different continents. The wide-ranging impact underscores the critical need for organizations worldwide to strengthen their cybersecurity defenses and implement robust measures to protect their Fortinet devices. The ongoing threat requires constant vigilance and proactive security measures to prevent a successful breach.
Recommendations for Fortinet Users
In light of these attacks, Fortinet users are strongly advised to take immediate action. Organizations should ensure all their Fortinet SSL VPN and FortiManager devices are patched with the latest security updates to mitigate any known vulnerabilities. It is also crucial to enforce strong password policies, including multi-factor authentication (MFA), to make brute-force attacks significantly more difficult to succeed. Regular monitoring of network traffic for unusual activity and implementing intrusion detection systems can help in identifying and blocking such attacks in real-time. Proactive measures like these are essential to defend against sophisticated, targeted campaigns like the one currently underway.
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