IT'S a filthy habit which could leave you at risk of catching a nasty virus.

Porn watchers have been urged to check their computers immediately after "millions" of grubby sex vid fans were infected by a piece of malware called Kovter.

3 Porn lovers beware: there's an 'orrible virus on the loose

Researchers from the tech firm Proofpoint said that visitors to the wildly popular website PornHub are being tricked into downloading files which then infect their computer.

Users are first shown false pages offering updates to software such as Google Chrome or Firefox.

But when they download these updates and open them up, their systems become infected by the Kovter virus.

This malware is known as a "malvertising" attack because it works to spread more dodgy adverts designed to snare other victims.

3 This is one of the fake pages designed to trick victims into downloading viruses

3 The pages look convincing but are actually expertly crafted traps. Anyone who downloads the files on the pages will probably be hit with malware

Once you've downloaded the dodgy file, it will infect your system and try to spread the virus to other people.

This type of malicious software is traditionally used as a form of online advertising fraud to generate money through clicks on fake adverts.

In some cases a "clickbot" is installed which then requests and interacts with random adverts online.

In the case of Pornhub, Proofpoint said users were shown fake adverts urging them to click to download a new version or Flash update to their web browser - but would instead infect their computers.

The malware is capable of infecting all three major Windows web browsers: Chrome, Firefox, and Microsoft Edge/Internet Explorer.

Proofpoint warned that this technique of tricking users into clicking on fake adverts and infecting themselves was effective, and had the potential to reach "millions of web surfers" if used elsewhere.

"Campaigns on very high-ranking websites... that convince users to infect themselves means that potential exposure to malware is quite high, reaching millions of web surfers, " Proofpoint wrote.

Mark James, a security specialist at a tech firm called ESET, said that porn was a great way of spreading dodgy viruses.

"When you target areas like PornHub, your chances of success may be higher," he said.

"The audience is possibly less likely to have security in place or active as people’s perception is that it’s already a dark place to surf.

"Also the user may be less likely to call for help... not wanting others to see their browsing habits- and of course the criminals are fully aware of this."

Earlier this year, porn lovers were told that visiting X-rated websites on their mobile phones could expose their filthy secrets to the world.

Adult websites are much more likely to expose your viewing habits if they're accessed on a mobile, the tech firm Wandera said.

It was recently claimed that porn could be ruining your sex life by "peddling the myth it’s easy to make girls orgasm".

Experts analysed PornHub's 50 most watched films of all time and found only 18 per cent of women reached an orgasm.

Yep, you guessed it - the rest were fake.