Fortinet VPN Under Siege: 13 Million Brute Force Attacks Expose Enterprise Weaknesses

On January 31, 2023, cybersecurity researchers at GrayNoise revealed a staggering escalation in attacks targeting Fortinet SSL VPN devices. More than 13.5 million login attempts had been recorded exploiting CVE-2022-42475, a heap-based buffer overflow vulnerability in FortiOS SSL-VPN that allows remote unauthenticated attackers to execute arbitrary code. The scale of the assault, coupled with a newly discovered zero-day in GoAnywhere MFT file transfer software, painted a sobering picture of the threat landscape facing enterprises and crypto businesses alike.

The Threat Landscape

The Fortinet VPN vulnerability, disclosed in December 2022, became one of the most aggressively targeted flaws in early 2023. By January 31, GrayNoise observed 13,513,728 login attempts against devices running vulnerable FortiOS versions. The vulnerability exists in the SSL-VPN web interface, which is typically exposed to the internet to enable remote access. This makes it an ideal target for attackers seeking initial access to corporate networks, including those of cryptocurrency exchanges, wallet providers, and blockchain infrastructure companies.

Simultaneously, security researchers warned that a zero-day vulnerability in Fortra GoAnywhere MFT, a managed file transfer solution used widely in enterprise environments, was being actively exploited. The flaw resided in the administrative web interface and could be leveraged for remote code execution through specially crafted requests. No patch was available at the time, leaving organizations reliant on the platform exposed. The combination of these two attack vectors created a particularly dangerous window for organizations handling digital assets.

Core Principles

Defending against these threats requires adherence to several fundamental security principles. The first is timely patching. CVE-2022-42475 had a patch available for weeks before the January spike in exploitation, yet many organizations had not applied it. The second principle is network segmentation. VPN appliances should not be directly exposed to the internet without additional protective layers such as web application firewalls or access proxies. The third principle is credential hygiene. Many of the 13.5 million attempts were brute force attacks relying on weak or default credentials.

For cryptocurrency businesses, these principles carry additional weight. A compromised VPN gateway can provide attackers with a foothold into internal networks where private keys, hot wallet credentials, and administrative systems reside. The FBI had just days earlier announced its takedown of the Hive ransomware operation, which had extorted over 100 million USD from more than 300 victims. That success, while significant, did not eliminate the underlying vulnerabilities that ransomware groups exploit to gain initial access.

Tooling and Setup

Organizations looking to strengthen their defenses should implement a multi-layered approach to VPN and remote access security. Start with an inventory of all internet-facing remote access points, including VPN appliances, remote desktop services, and file transfer platforms. Apply all available patches immediately and subscribe to vendor security advisories for critical infrastructure components. Deploy multi-factor authentication on all remote access systems, preferably using hardware tokens or authenticator apps rather than SMS-based codes which are vulnerable to SIM swapping.

Network monitoring tools should be configured to detect anomalous login patterns, such as the high-volume brute force activity seen in the Fortinet attacks. Rate limiting and account lockout policies can mitigate automated credential stuffing. For GoAnywhere MFT and similar platforms, restrict access to the administrative interface to trusted IP ranges and consider placing it behind a VPN or zero-trust network access solution until patches become available.

Ongoing Vigilance

Threat landscapes evolve rapidly. The GoAnywhere zero-day demonstrated that even fully patched systems can be vulnerable to newly discovered flaws. Organizations must maintain continuous monitoring, threat intelligence feeds, and incident response readiness. Regular penetration testing of external-facing infrastructure helps identify weaknesses before attackers do. Bitcoin was trading around 23,139 USD on this date, and the broader crypto market recovery was attracting renewed attention from both investors and threat actors.

The convergence of IT and operational technology in blockchain environments means that a vulnerability in a traditional enterprise tool like a VPN can have outsized consequences when it provides access to cryptocurrency infrastructure. Security teams at crypto firms must extend their visibility beyond blockchain-specific threats to encompass the full spectrum of enterprise vulnerabilities.

Final Takeaway

The Fortinet VPN siege and GoAnywhere zero-day serve as a reminder that the basics of cybersecurity still matter enormously. Patching promptly, enforcing strong authentication, segmenting networks, and monitoring for anomalous activity remain the most effective defenses against both opportunistic and targeted attacks. As cryptocurrency markets grow and attract more institutional capital, the security expectations placed on crypto businesses will only increase. Those who invest in foundational security practices today will be better positioned to weather the next wave of threats.

Disclaimer: This article is for informational purposes only and does not constitute financial or security advice. Always consult with qualified professionals for specific guidance.