Hackers seeking to exploit the global interest in Barack Obama's sweeping election victory have bought their way to the top of the Google results page.
For most of Wednesday afternoon, searches involving the keyword "Obama" generated a sponsored link reading "Download Now" at the top of the results page. People who clicked on the link would reach a Web page infected with malicious software.
Security experts confirmed that the site could compromise PC users' security.
"The Web site is infected with a malicious i-frame," said Graham Cluley, senior technology consultant at the online security company Sophos. "This code then downloads further malware onto your PC, including something called Mal/Pdfex-B. Ultimately this code is designed to compromise your computer and allow hackers to have remote control over your PC."
Unlike early virus writers, who were motivated mainly by the desire for notoriety, today's hackers work for profit.
"We are also seeing a major malicious spam campaign featuring Obama at the moment, which points to a malware download," Mr Cluley said. "We're gathering information about that right now."