Open Source

Doesn't closed source help protect against crack attacks?

This is exactly backwards, as any cryptographer will tell you. Security through obscurity just does not work.

Closed sources is characterised by three bad things:

1. creates a false sense of security
2. means that the good guys will not find holes and fix them
3. makes it harder to distribute trustworthy fixes when a hole is revealed.

e.g. Microsoft Outlook Express