Lincolnshire Police are warning of a sophisticated e-mail bank scam.
The warning is the second time this year that police have urged people to be on their guard against the internet appeal.
Officers said various messages are being circulated asking e-mail users for confidential information.
Police said the e-mails look "extremely convincing" and include bank logos. The message asks for confirmation of passwords and pin numbers.
Officers say these e-mails are scams as a bank would not ask for sensitive information over the internet.
The messages are from fraudsters who use the information to break into accounts.