strongSwan is an open-source, modular IPsec-based VPN solution that implements the Internet Key Exchange (IKE) protocols. Organisations install it on their own servers and gateways to connect sites and remote users, which makes it an alternative to proprietary IPsec gateway appliances. The project is released under the GPLv2 and, besides the open-source code, offers commercial licensing options.
The project's intellectual property has belonged to secunet Security Networks AG since 2022. secunet is a German cybersecurity company headquartered in Essen, and the project website names it as a maintainer and main sponsor, alongside codelabs GmbH. The software runs on infrastructure that the organisation controls, so traffic and configuration are not sent to a vendor cloud. The source code is public, so a European organisation can review it, build it itself and maintain it under its own control.