Built for security
Strive to make our software robust and secure, and encourage companies to use whichever pieces they want to.
Pay attention to security problems and fix them before anyone else does.
Be as politics-free as possible; solutions should be decided on the basis of technical merit.
Do not let serious problems sit unsolved.
OpenBSD tracks and implements standards (ANSI, POSIX, parts of X/Open, etc.)
So good interoperability and no vendor lock-in!
The firewall component of OpenBSD is called pf (packet filter).
It offers a comprehensive suite of features and is so well regarded that it has been ported to many other operating systems.
Apple uses it in MacOS and in iOS. And BlackBerry uses it in the BlackBerry 10 operating system. Pf is also used in FreeBSD, DragonFly BSD, Debian GNU/kFreeBSD and Oracle Solaris.
However OpenBSD is the native platform for pf so the OpenBSD version of pf is always newer and more advanced than other platforms.
The advantage of Open Source software
The open software development model permits the OpenBSD developers to take a more uncompromising view towards increased security than most vendors are able to. They can make changes the vendors would not make.
Open Source software is not easily subject to interference by nation states or hackers.