Re: Free
That's a major problem with Open Source. If you have unlimited resources then the code is there for you to find new holes in. If the code is proprietary / not public then you have to reverse engineer it and / or fuzz it which is a far more difficult undertaking.
For instance current Windows version OS code may not be any more secure than Linux but it had fewer publically known vulnerabilities in the last year than just the Linux kernel, let alone a full Linux distribution....