Choosing secure passwords
Many believe that Linux is inherently more secure than the other platforms. While there is an endless debate on either side of this argument, no inherent security can save you if you use weak passwords on your system. What it all comes down to is that having a simple password based on a simple dictionary word would be broken by a cracker in just a few minutes, regardless of how secure your kernel is. A longer password with special characters and differing capitalization may be more difficult to type, but it would be harder for someone to guess it by launching a brute-force attack.
One useful tool that checks the strength of your password is the Password Haystacks tool found on the Gibson Research Corporation website. While it is not specific to Mint or even Linux, it's a very useful tool you can use to check the strength of your password. There, you can type in the password you're considering to see how conceivably strong it is against different attack...