IT security experts warned today of a "widespread phishing email campaign" that tries to swindle unwary recipients by pretending to offer a cash prize from Gmail, Google's popular free email service.

The emails claim that the recipient has been randomly selected for a $500 cash prize, and that the money can be paid automatically if they click on the embedded web link. Part of the email reads as follows:

'You won $500! Gmail congratulates you!
CONGRATULATIONS!
YOU WON $500!
Gmail gives members random cash prizes. Today, your account is randomly selected as the one of 12 top winners accounts who will get cash prizes from us. Please click the link below and follow instructions on our web site. Your money will be paid directly to your e-gold, PayPal, StormPay or MoneyBookers account.'

The embedded link takes users to a web page saying that there has been a problem sending the payment. They are then asked to enter their bank details and pay a membership fee of $8.60.

"Of course this email wasn't really sent by the folks at Gmail, and the $500 cash prize doesn't exist. Anyone tempted to try and collect it is in danger of walking straight into a trap set by these fraudsters," said Graham Cluley, senior technology consultant at Sophos.

"People need to learn that there is no such thing as a free lunch, and be much more wary of unsolicited email communications whoever they may appear to come from."

Sophos revealed in a survey earlier this year that 58 per cent of people receive at least one phishing email every day.