A large enterprise client found themselves staring down the barrel of a critical security and operational deadline. Their primary perimeter firewall, an aging Fortinet device, had officially reached end-of-support, putting compliance and security posture at risk. But the true problem wasn’t the hardware; it was what lived inside. Over years of incremental growth, nearly 2,000 IPsec VPN tunnels had been created to support vendors and third-party business operations. Documentation was inconsistent, and most critically, the pre-shared keys (PSKs) for these tunnels were unrecoverable by conventional means.
Upgrading to a newer, supported FortiOS version was non-negotiable. Yet modern firmware no longer handled tunnel PSKs in the same way, making a direct upgrade impossible. The only traditional option was a months-long process of manually rebuilding thousands of tunnels, renegotiating PSKs with every external partner, and coordinating countless maintenance windows, all while exposing the client to SLA risks and operational disruption. Their requirement was bold and nearly impossible: replace the legacy firewall in a single maintenance window with no downtime, no vendor coordination, and no operational impact.
December 2020
Telecommunications
Cost avoidance
At THIRD SPECTRUM, impossible is where we start. Rather than accept the limitations of conventional migration strategies, we looked for unconventional opportunities within the legacy FortiOS.
Armed with insight, our team engineered a bespoke migration pathway. After decompressing the firmware, we isolated the binaries responsible for encryption routines and confirmed both the static key and the cipher. From there, we developed a custom toolset that could parse the old firewall configuration, locate encrypted PSKs, decrypt them with the recovered key, and generate a modern FortiOS-ready configuration file.
Our tooling did more than decrypt, it sanitized, validated, and structured the converted configuration to ensure that no syntax errors or logical conflicts could disrupt the import process. In effect, it transformed legacy complexity into modern compatibility.
The final phase involved rigorous lab testing, staging, and validation before executing a precise cutover plan. On migration night, the new firewall was deployed with a complete, validated configuration, seamlessly inheriting nearly 2,000 tunnels. The cutover was invisible to business operations—exactly the outcome the client needed.
The impact was both technical and strategic. The migration of nearly 2,000 tunnels was executed cleanly, with zero downtime and no need for external vendor coordination. What could have been a months-long nightmare was compressed into a single, flawless maintenance window.
The client decommissioned unsupported hardware, modernized their security perimeter, and maintained compliance without any business disruption. Cost savings were immense, not just in avoided labor, but in preventing SLA penalties, minimizing operational risk, and preserving critical vendor relationships.
Most importantly, the solution was executed ethically and defensively. The CVE was leveraged only within the client’s environment, ensuring compliance and legal safety. No external systems were touched, no boundaries crossed.
At THIRD SPECTRUM, this is what we do best, turn “impossible” into executed reality. From legacy migrations to gray-zone reverse engineering, our team combines deep technical mastery with pragmatic execution to deliver outcomes others won’t even attempt.
