Web Malware Infects Fast, Dies Young

The life cycle of Web-based malware has become so quick that infected sites often disappear before anyone can shut them down.

Just in the past three months, security researchers at AVG Technologies have seen the number of new infected Web sites grow by 66%, from 100,000 to 200,000 per day to 200,000 to 300,000 per day. And the company's researchers expect the trend to continue.

Google has noticed a similar, if less pronounced, trend in spam. The company reported Monday that spam volume rose 25% in 2008 compared with the amount recorded in 2007.

And because there are more infectious sites, cybercriminals can afford to have them active for less time. Roger Thompson, chief research officer for AVG, said he was astonished to find how transient malware has become. Almost 60% of infected Web sites disappear in a day or less, he said.

Such tactics, he said, represent an attempt to confound efforts by Google and other Web companies to compile malware databases. He estimated that Google reindexes the average Web site once every four days. Such sites can become infected and then clean again before anyone notices.

These Web threats are no less dangerous for their abbreviated lives. Indeed, Thompson said the risks are greater now. "It used to be you only got into trouble if you went to sites of ill repute," he said.

Now, thanks to mass SQL injection attacks and other techniques, even well-regarded legitimate Web sites may be compromised to host to malware.

One reason malware has moved to the Web, said Thompson, is Windows XP SP2, which shipped with its firewall turned on by default. That drove cybercriminals to attack through the Web browser, which is allowed through the firewall.

To defend against online malware, Thompson said that signature-based systems aren't enough anymore. He recommends an approach he likens to layering slices of Swiss cheese -- no computer security is perfect, but with enough layers, the holes disappear. It may just be coincidence but AVG makes such software.

In any event, there's no guarantee of safety because cybercriminals continue to refine social engineering attacks that dupe users into taking harmful action.

"There's no patch for foolishness," Thompson said.