Malware continued to dominate the threat landscape in the second half of 2009, and Trojans were the most common type of threat, according to the latest Microsoft Security Intelligence Report.
The company collated data from over 500 million computers worldwide using sources such as its Forefront and Defender security products, Malicious Software Removal Tool, Bing and Windows Live Hotmail.
Microsoft found that malware accounted for 69.9 per cent of all threats detected on infected computers in the period, up from 67.1 per cent in the first half of the year.
However, the number of malware-infected PCs dropped during the period, from 4.9 to 4.1 out of every 1,000.
"The Security Intelligence Report Volume 8 provides compelling evidence that cyber criminals are becoming more sophisticated and packaging online threats to create, update and maintain exploit kits that are sold on to others to deploy," said Cliff Evans, head of privacy and security at Microsoft UK.
"Malware creators are continually improving their 'products' by replacing poorly performing exploits with new ones."
The report also found that most of the threats faced by companies can be tracked back to a handful of botnets. The top five botnets were responsible for sending more than 94 per cent of all spam during the period, for example.
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