Microsoft's latest report says nearly half of computer infections are caused by users.

Microsoft released a security intelligence report for the first half of 2011 that only 5.6% of malware infections were caused by security breaches, and 45% were caused by users themselves.

It is reported that computers worldwide have an average of 9.8 infections per 1,000 units. Malware uses USB<automatic running> functional infections account for 26% and file distribution accounts for 4.4%. Password attacks accounted for 1.7% and 0.3% of Office document infections, respectively.

The number of infected computers in the UK has declined. From 7.4 units per thousand infections in the third quarter of 2010 to 5.2 infections per thousand in the second quarter of this year. Malicious adware infection accounted for 49.1%, malicious Trojan software infection accounted for 31.9%, up 5%. Another 27.9% of infections are due to the software that may not be needed.

The top ten malwares containing Trojan viruses are: Win32/FakeRean sixth, Alureon tenth. ZeuS was included in the top ten malware in 2010 and was replaced by Conficker in 2011.

Microsoft Security Intelligence reports data from more than 600 million systems in 100 countries using Microsoft malware removal tools.