Computer hackers have stepped-up their efforts to target unsuspecting online bank customers.
Internet security firm Symantec said it had noticed a huge jump in attempted phishing attacks in the second half of last year.
The company filters millions of emails a day on behalf of companies around the world.
In July last year the firm's anti-virus software was preventing around nine million emails containing a phishing attack from getting through to intended victims per week.
Within six months the number of phishing attacks blocked had soared to an average of 33 million a week, according to the report.
A typical phishing attack starts with a spoof email directing users to a fake website for their bank.
Fraudsters try to trick customers into giving away their log-in detail or other personal information.
One in every 250 email messages filtered between July and December last year contained a phishing attack, according to the report.
The firm also reported a continuing problem with junk emails - otherwise known as spam.
More than 60 per cent of emails filtered during the six months were classified as spam, said the report.
Symantec also highlighted the growing threat from software which infects computers with the intention of relaying information on what tasks the user performs back to hackers.
So-called "spyware" has been used in the past to obtain password information based on the order in which users press keys.
Richard Archdeacon, director of technical services at Symantec, said: "New forms of attack that use underhand and subtle methods like phishing and spyware are becoming increasingly prevalent.
"We predicted in our previous Threat Report that these methods would become more popular with attackers and this has proved to be the case, with spam in particular and phishing emails to a lesser extent becoming a way of life for every computer user today.
Meanwhile, consumers who bank online have been warned about the latest security threat - viruses that re-direct users to fake banking and finance websites.
Barclays' and Bank of Scotland's websites are the most recent to have come under attack from so-called " pharming" attacks, according to European communications portal, Lycos UK.
Lycos has been tracking a substantial rise in the virus, known as Troj/BankAsh-A, which can be used as part of these attacks.
The company said its antivirus filters had stopped 39,789 incidents of the virus since it first appeared on the internet, 34 days ago.
While this is a relatively low number, the virus has the potential to cause massive financial damage to anyone who inadvertently installs it on their PC.
It works by getting downloaded onto a users' machine - delivered as an email attachment, as a download from a webpage or file-sharing network, or is placed on the users' PC as part of another software package.
The virus lies dormant until the user accesses the internet and attempts to go onto a banking website. Instead of being directed to the real bank website, the user is sent to a fake website, designed to look like the real thing. Criminals use the data entered - user names and passwords - to commit fraud on the users' real bank account.