Cybercriminals are changing tactics by using malicious software as a tool for profit, and the trend is set to increase as hacking becomes easier.
A security intelligence report by Microsoft has found that detection of malicious software rose by more than 300percent from the second half of 2006 to last year.
Malicious software, also known as Malware, is designed to infiltrate or damage a computer system without the owner's informed consent.
Colin Erasmus, security specialist at Microsoft, said yesterday: "We found that when a computer crashes, is slow or doesn't work properly, 80percent of the time it was because of presence of Malware.
"There is plenty of Malware out there and much of the time people ask for it to be installed in their machines, strange as it may seem," said Erasmus.
When people register for certain services, membership and social networking they are often asked to fill in a checkbox that they have read a disclaimer.
On many of these websites people rarely read the disclaimer in full and unwittingly consent to the damaging software on their machines.
"You then have pop advertising when you log on, often from pornography websites," Erasmus said.