The IT Department where Daniel Toth works won't let him use open source software because they believe it's a security risk. Is it?
No. If anything, open-source software has the potential to be safer. Not that it always is, of course.
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 favourite 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.
And it's not as if closed-source programs are especially secure. People find exploits in Windows all the time.
Back in 1999, security expert Bruce Schneier wrote that "Public security is always more secure than proprietary security...For us, open source isn't just a business model; it's smart engineering practice." (I checked with Schneier while researching this piece; he still stands by those words.)
But don't be too hard on your IT department. They have to approve every program put on company computers, and checking out new programs is time-consuming. Open-source or not, they don't want programs on their PCs that they haven't vetted, and they don't have time to research or test everything. Besides, they may have to answer to executives who think that k is an effective password.