Police today warned World Cup football fans not to try to buy tickets from websites such as eBay and Gumtree.
Fifa, the competition organiser, said some "unscrupulous individuals" were using websites to try to profit from fans who are desperate to see their team.
Paper tickets will only be printed a few weeks before the competition starts and must be collected in person from collection points in South Africa.
Rules state that tickets are also only to be used by the ticket holder named at the time of purchase.
A spokeswoman for Scotland Yard's central e-crime unit said: "Tickets will only be issued in South Africa for the World Cup.
"So anyone claiming to be able to supply tickets will be either supplying counterfeit tickets or nothing will be received.
"Given that tickets for the World Cup can only be collected in South Africa, it appears that any site offering tickets will have criminal intent."
Fifa said in a statement on its website: "While genuine tickets are sold online exclusively via the official website Fifa.com , unscrupulous individuals are taking advantage of the great appeal of this event by trying to use the internet to sell tickets they do not possess.
"A special team from Fifa's legal affairs division is working closely with international authorities to monitor the internet for such illegal offers and to take action to combat them."
A listing on auction site eBay today was offering a pair of seats for each of Italy's three opening games with a "buy it now" price of 5,500 US dollars.
Nobody had opened the bidding at the desired price of 5,000 US dollars.
A seller on Gumtree said he had 24 first round game tickets to sell at £90 each.
The sites said they take moves to prevent such listings.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies