Websites running Microsoft's Web server software are twice as likely to be hosting malicious code as other websites, according to research from Google.

Last month, Google's Anti-Malware team looked at 70,000 domains that were either distributing malware or hosting attack code and made the finding. "Compared to our sample of servers across the Internet, Microsoft IIS features twice as often as a malware-distributing server," wrote Google's Nagendra Modadugu, in a Tuesday blog posting.

Together, IIS (Internet Information Services) and Apache servers host about 89 percent of all websites, but collectively, they're responsible for 98 percent of all Web-based malware. Google actually found an equal number of Apache and IIS websites hosting malicious software, but because there are so many more sites hosted by Apache servers (66 percent versus Microsoft's 23 percent), malicious sites make up a much larger percentage of all IIS servers.

Modadugu didn't draw any conclusions about whether this means that Microsoft servers are more likely to be hacked. "It is important to note that while many servers serve malware as a result of a server compromise ... some servers are configured to serve up exploits by their administrators," Modadugu wrote.

Google also found that the malware server of choice varied from region to region. In China and South Korea, for example, the majority of malicious websites are running IIS. In the US, Russia, and Germany, however, Apache is the predominant malware server.

Modadugu speculated that the servers in China and South Korea may be running pirated software and thus unable to get Microsoft's latest security updates.

According to one security researcher, the fact that IIS is so easy to use may account for Google's findings. It's easier to operate an ISS Web server than an Apache Web server, said Cesar Cerrudo, chief executive of security research firm Argeniss. "People who are not too skilled will install Windows and set up a Web server with weak configuration."

But Cerrudo said that more information would be required to draw any solid conclusions about the security of IIS. "The report says that 70,000 domains were examined, but what about if 5,000 domains are in the same Web server in China?" he asked. "It's pretty easy playing with numbers and concluding. A lot of more data is needed to get the right conclusions."

Microsoft and Apache did not immediately respond to messages seeking comment.