According to Russian antivirus company Kaspersky Labs, these criminals are behind 90 percent of malicious code, leaving teenagers and script kiddies responsible for only a small fraction of total malware.
"There's a lot of money in the Internet," said Eugene Kaspersky, head of antivirus research for Kaspersky Labs, on Thursday. "On the last count of malware I did, only 10 percent was written by teenagers. Ninety percent is developed by criminals. This malware is designed for criminal needs, such as stealing money, distributing spam and Internet rackets."
Criminals are turning to the Internet because of the lack of security and policing, Kaspersky said. "It's getting more serious because many attacks are being developed by professionals. It's not such good news because they have brains and they are getting more experienced."
Kaspersky warned that Trojans, which open back doors on computers for hackers to enter through, have become easy to develop and are being used to steal banking details from users. He said that Trojans sit on a computer, waiting for a user to browse a Web site with the word "bank" in it. At this point, the Trojan records the user's key strokes, capturing their user name, password and account numbers.
"If you type in your login and password, you don't need to worry about your money any more," said Kaspersky. "Sometimes it's not possible to get the money directly, so they buy something cheaply on the Internet then sell it on."
Kaspersky highlighted the Brazilian hackers that were arrested earlier this year. Between them, the hackers stole around $80m from Brazilian users, which Kaspersky said was a simple task. "I see this is a very good business," said Kaspersky. "It's easy to attack Internet banks."
He added that press reports of the hackers' success had worked as an incentive for more hackers to try the same thing. "Now we have more Trojans [aimed at Brazilian users]. This is a criminal business and it works."
Zombie networks of computers, known as botnets, are available to buy over the Internet, Kaspersky added. "There was a Web page with one for sale -- an Internet shop for zombie networks with 5,000 machines for $300."