Gmail users have been urged to check their accounts after it was revealed that more than 183 million passwords were stolen in a data breach.  

Australian cyber expert Troy Hunt, who revealed the incident, called it a 'vast corpus' of breached data, which totals 3.5 terrabytes. 

To put that into perspective, that's the equivalent to 875 full-length HD movies. 

According to Mr Hunt, 'all the major providers have email addresses in there' – so not just Gmail, but Outlook, Yahoo and others too.

'They're from everywhere you could imagine, but Gmail always features heavily,' Hunt told the Daily Mail. 

So have you been caught up in the incident?

Here's how to check if your email data has been compromised. 

The incident occurred in April but has only just been disclosed on Mr Hunt's Have I Been Pwned (HIBP) website. 

According to the expert, breached data contained 183 million unique email addresses alongside the websites they were entered into and the passwords used. 

To check if you've been compromised, head to the Have I Been Pwned website and enter your email address in the search bar. 

Next, tap on the button marked 'Check' and the site will show you the list of data breaches affecting your email address.

Even if not included in the recent Gmail breach, your details may have been involved in past breaches going back over a decade. 

If you are one of the 183 million people affected in this latest incident, you need to change your email password as soon as possible. 

Once this is done, enable two-factor authentication (2FA) if you haven't already – which sends a code to your smartphone to get into your online accounts.

According to Mr Hunt, this incident is not a single breach but a collection of 'stealer logs' – a series of data files generated and compiled by 'malware' (malicious software).