Criminal gangs are duping car buyers out of millions of pounds each year by using adverts on reputable trade websites, BBC News reported.
The virtual vehicle scam also involves fake shipping websites that promise to safeguard the buyer's money.
The Metropolitan Police say 21,000 fraudulent sites were shut down in the UK last year.
The Met warns that unless buyers see the car for themselves, it is likely to be an offer that is too good to be true.
According to the BBC, criminals will place an advert on a reputable website, like Auto Trader or E-Bay, but for a vehicle that does not belong to them.
But the ad looks legitimate and the websites themselves are none the wiser.
Then, the fraudsters direct you to another website that is supposed to look after your cash until the car is shipped to you.
But this one is fake and the money goes straight into their bank accounts.