An open-source program is one whose source code is open to anyone who wishes to study it--or improve upon it. Open-source software is usually free and often public domain. Popular open-source programs include Linux, OpenOffice, and a program you're quite likely using to read this blog post: Mozilla Firefox.
I might also add that two of my favorite security programs, Password Safe and TrueCrypt, are open source. I wouldn't trade them for anything.
At first glance, this seems counter-intuitive. If any hacker can read your code, why can't they use that knowledge against you? Think of what the Rebel Alliance did with the Death Star plans in the original Star Wars.
Reality and Star Wars don't always coincide. When everyone has access to the source code, a great many experts are able to examine that code thoroughly and determine if it really is secure. That's prohibitively expensive if the only people with access to the code are on the payroll.
The link for this article located at IT World is no longer available.
