Interland, the world's second-largest Web-hosting company, appears to have suffered an ongoing mass hack attack that has compromised some 1,100 websites, according to a security professional who has analyzed the script.

Marc Maiffret, a co-founder of eEye Digital Security, said the sites have been infected with a malicious script that continues to reinfect them after they are cleaned. The hack has also placed visitors to the compromised sites at risk of being infected by malicious code, he said.

But Interland denies that a hack has occurred, saying only that a few sites have gone offline.

According to Maiffret, Web surfers who have visited the compromised sites might get a surprise on their next phone bill when they discover expensive calls made to 900 numbers. Others could also find themselves party to a denial-of-service attack launched against another computer.

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