Eric Raymond is one of the premier supporters of Open Source Software Development. His site at opensource.org is a warehouse of useful information. It's a central part of our engineering tradition, part of our working method almost by instinct. We all know how astonishingly reliable the running gears of the Internet are relative to their nearest commercial equivalents. The bad guys will find the holes whether source is open or closed.
Closed sources do three bad things.
Open source ensures that your code is submitted to the most harsh and penetrating peer review possible. Such reviews include bug checking , security attacks , and benchmarking. If a bug is detected, it is usually detected by a friend first. The security through obscurity of closed source is only an illusory veil of security. Security hole announcements in such closed systems as Windows NT have been as regular as those announced for open source code such as sendmail.