The search engine Pwned will tell you if your account has been hacked. In recent years a lot of services got hacked, we all remember Yahoo!, Dropbox, Adobe, LinkedIn and more. Have I been pwned is the place for you to check if your account from one of this services is compromised.
How does this site know if your Email account is linked with one of those services ?, Easily, researchers found more than 500 million accounts on few servers that for some reason those servers not even secure. Someone took all the data from the big breaches from the recent events and put them all together.
Enter your Email and check if you need to change password right now, We always recommend to be on guard and change passwords from time to time.
The site itself is very easy to use as you just need to enter your mail. You can also ask the site to notify you if your account appears on new breaches.