Over 1 per cent of search results include malicious sites

Google research paper confirms significant increase in number of malware-serving websites.

Recent reports of increasing numbers of websites serving malicious content have been confirmed in a paper published by researchers from Google.

The researchers report finding over three million URLs serving malware, as detected by at least one anti-virus program, with another three million showing suspicious behaviour. In most cases, the malware is loaded into the page via a piece of JavaScript code or via an iframe linking to an external site, with almost 10,000 sites found to be actually hosting the malware.

Though these numbers may seem insignificant among the billions of websites on the internet, more than 1% of all Google search results pages now contain at least one site serving malware, a figure which has quadrupled in the past nine months.

Not surprisingly, users who visit websites with adult content have a higher risk of running into malware. However, this does not mean that these are the only sites that pose a threat, as malware was found on every type of website, according to the Open Directory Project categorisation of websites. In fact, most malware-serving websites are genuine sites that have been compromised. This may be partly the fault of website administrators, as over 38% of malware-serving websites that run the Apache server software use an out-of-date version, with another 26% not reporting their version number. 40% of the PHP versions in use were also found to be out of date.

The researchers also looked into the global distribution of malicious websites. Of the sites serving malware, as well as of those actually hosting the malware, two thirds are located in China, with the United States and Russia taking second and third place in both categories. However, these figures vary greatly from country to country. For instance, for 96% of Chinese websites serving malware, the malware is also hosted in China.

The paper confirms a worrying trend of increasing numbers of genuine websites serving malware, and implies that the former 'safe browsing' strategy of visiting only trusted sites is fast becoming impossible to implement. Web users can protect themselves by ensuring they run reputable security software and keeping it updated, and web administrators must ensure they run up-to-date versions of server software and keep their sites clean.

A summary of findings can be found at Google's Online Security Blog here, while the original paper can be downloaded (in PDF format) here.

12 February 2008

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