GOOGLE has warned users that billions of passwords – and hundreds of thousands of username and password combinations – have been hacked.
Cyber-experts are now urging users to make sure they're using tough passwords that haven't already been stolen.
Earlier this year, Google launched a Password Checkup add-on for the Google Chrome web browser.
It displays a warning whenever you sign in to a website using "one of over 4billion usernames and passwords" that have been hacked.
Google does this by cross-referencing your log-in details for different sites with a huge list of hacked log-ins.
"Since our launch, over 650,000 people have participated in our early experiment," Google's Jennifer Pullman explained.