Renowned for being stable and standards compliant.
Little known fact is that Apple's Mac OS X is a BSD based operating system, even less known is the fact that Microsoft copied the BSD TCP/IP stack code into their products rather than writing their own (it does not go down too well with their policy of claiming that open-source is evil and of poor quality).
Why do so many people use or copy from BSD? Because of its license, the BSD licenses do not restrict users in any way: you are allowed to copy, modify, sell, etc. All without having to contribute back to the authors or to the end user
See how they relate to the Unix History genealogy

BSD based operating system are usually very secure by default, unfortunately there are some important issues to be aware of:

  • Due to the comparatively small number of targets for attackers, some believe that it actually helps in protecting them.
    It may slow down the spread of a virus or worm because of the amount of unsuccessful attempts before it finds a compatible target but that is largely irrelevant, and it is also clear that virus writers are more likely to prefer some more widely available targets as it will have a much bigger impact.
    However, "security by obscurity" has never fixed bugs or stopped anyone exploiting them. Again, complacency becomes the worst enemy...
  • and exposed the fact that Mac OS X is not a secure as Apple would like you to think... by a long shot.


Just like Linux, BSD operating systems come in many flavours


How to make BSD systems more secure


Where to get more information