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Warnings spreading across social media sites about a Christmas tree virus are well-intentioned but, apparently, a hoax.

Online friends have been posting alerts and tweets about an app that allegedly will crash a computer. "Geek Squad says it's one of the worst Trojan viruses there is and it's spreading quickly," at least one version of the frantic warning states.

Yet technical support chain Geek Squad has issued no such statement, according to urban-legend site Snopes "Although anyone could at any time create a rogue application with the name 'Christmas Tree,' of course, we're not aware of any malware which uses this disguise," said Graham Cluley, senior technology consultant at Sophos, in a company blog. "Wouldn't you be more sensible to check with an established antivirus company? A legitimate warning would at the very least have included some links to further information -- such as a statement on Geek Squad's website."

While the non-existent malware can, of course, do no harm, antivirus makers are concerned that the message will live on in cyberspace, potentially drowning out important messages about future real threats.

"Ironically, the hoax is probably spreading much faster than any of the genuine commonly encountered Facebook viruses at the moment. Malware can be killed off fairly easily, but misinformation like this can live on for months, if not years, because people believe they are 'doing the right thing' by sharing the warning with their friends," said Cluley. "Please don't share virus warnings with your online friends until you have checked them with a credible source (such as an established computer security company)."