A report by security company Sophos indicates that 44.8 percent of all infected sites are hosted in China (including Hong Kong). That's more than twice as much as the 20.8 percent infected sites that are hosted in the U.S.
The number of infected Web pages has also grown. Sophos said that it detected an average of 5,000 new infected pages each day in the month of August.
The company warned that simply staying clear of sites hosted in the top three countries of China, United States and Russia was not effective in avoiding malware.
Said Carole Theriault, Sophos senior security consultant, in a statement: "While more than three quarters of infected Web pages are hosted in just three countries, that doesn't mean you only get hit if you visit Web sites based in those areas.
"Hackers are hijacking Web sites around the world to make them point to malware on sites based in China, the United States and Russia. Cybercriminals don't discriminate when it comes to targeting the Web," she added.
Sophos also warned against a sharp rise in spam pointing people to these infected sites. Malicious senders, in an attempt to bypass attachment virus scanners, are using messages that direct users to Web sites with malicious code. Computers get infected when users click on the links in the e-mail message.