Web security provider Symantec is warning of an email scam offering Facebook shares below their market value.
The scam claims to be sent from a finance firm with offices in London, Hong Kong, and Dubai, yet the phone number included in the message is based in Sacramento, California, said spokesman Nick Johnston.
The scam mentions loaning money under "soft'' or generous terms to buy Facebook stock or shares, then selling them back to the finance firm at a price higher than the original purchase price, he said.
A strong indicator of the scam is the email address which the scammer is asking to be replied to, a common, free web-based email provider.
A legitimate company would almost certainly use an email address at its own domain said Mr Johnston.
The subject title of the scam is "FACEBOOK (IPO) SUBSCRIPTION PARTNERSHIP PROPOSAL'' and the uppercase heading is a another common hallmark of email scams.
Martin Cocker from New Zealand cyber safety organisation Netsafe said the scam comes as "absolutely no surprise'' because scammers often target topical subjects.
Anyone who replied to the scam is advised to contact their bank to cancel any transactions they may have made.
Since Facebook launch four days ago shares have fallen more than 18 per cent to $34 US a share.