Security start-up Dasient says more than 640,000 websites, for a total of 5.8 million pages, were infected were infected with malware between July and September of this year.

Dasient, which specialises in combating malware on websites, identified more than 52,000 specific web-based malware infections, making a total of 72,000 unique infections it has catalogued since the company launched earlier this year.

"There are about 7,000 sites infected every day," says Dasient cofounder Neil Daswani. Dasient has also observed that the reinfection rate on websites that have been cleaned up is 39.6%. Attackers use automated scripts or malicious advertisements, among other means, to continually seek to load malware onto sites to perpetrate criminal schemes.

In addition to research on website infections, Dasient says it is making available "malware strings" composed of some attack code so IT managers can examine it with the goal of determining whether their sites might be infected.