A FREE tool that tells you if you've been hacked has been launched by Firefox browser firm Mozilla.
You can use it to immediately check whether your passwords have been exposed – and even receive warnings if it ever happens in the future.
Mozilla announced the tool earlier this year, and let some users test it over summer.
Now absolutely anyone can access Firefox Monitor, a free website that lets you check your online safety with a single click.
All you need to do is enter your e-mail address and you'll be warned if any of your accounts have been compromised.
And you can sign up on the site to get alerts if you're hacked at a later date.
The good news is that although it's being offered by Mozilla, it's available for anyone to use – even Google Chrome users.
"Data breaches, when information like your username and password are stolen from a website you use, are an unfortunate part of life on the internet today," said Mozilla's Nick Nguyen.
"It can be hard to keep track of when your information has been stolen, so we're going to help by launching Firefox Monitor, a free service that notifies people when they've been part of a data breach.
"After testing this summer, the results and positive attention gave us the confidence we needed to know this was a feature we wanted to give to all of our users."
So how does it work?
It's basically Mozilla's own version of an existing website called Have I Been Pwned.
When large websites – like MySpace or Tumblr – are hacked, the data is often leaked online – or sold through the dark web.
Have I Been Pwned collects all of that information and stores it in a giant database.
This database includes leaked emails and passwords from hundreds of different cyberattacks that have taken place over the years.
When you enter your email into Firefox Monitor, Mozilla encodes your email and checks it against an encoded database.
If your email matches an entry in the database, it means your account has been compromised and you'll be alerted.
Obviously the system isn't fool-proof: not every cyberattack will result in leaked details, so you may have been hacked even if Firefox Monitor gives you all the clear.
If you have been hacked, the first and most important thing to do is to change your password on the account that's been compromised.
For anyone who uses the same (or similar) passwords on multiple accounts, you should change your password for all of them.