Google has this 2 step verification to prevent your gmail account from being hacked.

Someone attempted to hack mine few months back and good thing I was able to use their 2 step verification. Basically in addition to your regular password, you have to enter a one time code generated on an app on your smartphone (iPhone, Android, blackberry).

For complete and detailed instructions, you can go here http://darktips.com/how-to-protect-y...-from-hackers/