Check to see if your email address or username has been published online after it was leaked in a data breach. Go to haveibeenpwned.com. Don’t panic if you do find your email address listed there, you’re in good company. At the time of writing, the site lists almost one and a half billion email addresses that have been published.
If your details are listed then change the password for the affected service, and any others that you’ve been using the same password for. That’s if you haven’t already changed your password to something a bit stronger.
If you’re a fan of nice visualisations you can have a look at all the breach data – with personal information removed of course – in a pretty dashboard here.
The point of HaveIBeenPwned.com is to illustrate how likely it is that your information has spilled out onto the web as a result of a data breach. There is no such thing as perfect security.