There are worries more and more people are falling victim to cyber criminals using fake anti-virus software. You think you're doing the right thing downloading programs supposedly designed to protect your PC. Instead the software's infecting your computer and stealing personal information.
One firm making genuine anti-virus programs has found more than 250 different examples of so-called "scareware" being sold online, for up to £60. It reckons 43 million people have fallen for the scam in the past year.
Rather than ridding a user's computer of viruses, many of the programmes contain malicious code that leaves the machine open to further attacks.
Some victims, who paid by credit card, also had their details sold-on and used to commit identity fraud.
"This has arisen in the past six months," said Dr David Wall of the Centre for Criminal Justice Studies at Leeds University.
"We knew of these packages before, but it wasn't so prevalent. It is quite a major issue now."
A typical scareware scam begins with a pop-up message, stating that an infection has been detected on the computer. Often this is supported by a fake scan of the machine.
Users are then invited to purchase bogus software that appears to fix the problem.
"It has got the look and feel of a professional piece of software," said Dr Wall.
"A lot of people download, pay for the upgrades, the problem appears to go away and that's it.
"They are not aware they have been scammed."
The report also claims that criminals are paying commission to intermediary websites, who refer customers to their fake software.
The owners of such sites can receive up to 35p for each successful download.
Some of the most popular pieces of scamware include SpywareGuard 2008, AntiVirus 2008, AntiVirus 2009, SpywareSecure, and XP AntiVirus.
Symantec, which carried out the study, recommends users purchase anti-virus and anti-phishing software from large, well known companies, including itself.
If you want to get protection without paying for it, there are also a number of free anti-virus programmes available online. They include AVG-Free and Avast! antivirus.