The hacker scripts try to infect site visitors and then attempt to use their compromised PCs to spread the infection to yet other sites.
Over the past month, the security services ScanSafe and Sophos have reported infections on such major Web sites as ColdwellBanker.com, Variety.com, and Tennis.com. Niels Provos reported in the Google security blog on June 3 that sites infected with Gumblar numbered about 60,000. Visitors became susceptible to infection simply by opening the sites in Internet Explorer.
After the script infects a PC, it attempts to spread its code to any Web site accessible via that machine’s FTP client, if one is present. Webmasters often use FTP to make changes to the sites they manage. If FTP software is configured to save a webmaster’s sign-in information, the malware can edit itself into a Web site’s pages.
Once a PC is running this class of malware, the hacker code tries to trick the user into opening infected PDF and Flash files. If the PC has an unpatched version of Adobe Reader, Acrobat, or Flash, opening an infected file can install a keylogger or other malware. In the case of Gumblar, Google search results in an Internet Explorer window are rewritten — in a way that end users may not notice — so the links point to hacker sites laden with infected PDF and Flash.
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