According to a new Microsoft security report, the prevalence of computer worms more than doubled during the first half of 2009, reports seattlepi.com. Since Microsoft's last Security Intelligence Report, worms increased 98.4 percent worldwide. IT Pro notes that the Conficker worm was the biggest driver for this resurgence.

Even though fewer users were infected from January to June, cyber criminals have gotten better at including extra malware in rogue applications. Jeff Williams, principal architect for Microsoft Malware Protection, says:

The result is that, from a criminal perspective, they're able to monetize in two ways instead of one. And from a user perspective, they have doubled the infection.

The report shows that Turkey, Spain, Brazil, Russia, Saudi Arabia, South Korea and Mexico had the highest rates of infection. The United States ranked in the middle.