Sophos researchers are warning of spam e-mails posing as confirmations of hotel reservations made at Booking.com.

The emails ask the receipient to open an attachment to view the details of the supposed reservation, but opening it isn't a good idea, according to Sophos' Graham Cluley. "The attached .ZIP file contains a Trojan horse designed to infect your computer," he writes. "Sophos products detect the malware as Mal/BredoZp-B and Troj/Inject-VI."

"As with similar hotel-theme scams, cybercriminals are simply banking on the fact that millions of people will be making hotel reservations in the upcoming months, and if they can trick just a fraction of those travelers into opening the rigged attachment, then they've succeeded," writes SecurityNewsDaily's Matt Liebowitz. "In this case, the attached file harbors a Trojan horse that for years has been worming its way onto people's computers and spying on their confidential information."

"Users should never open attachments sent out of the blue, especially from unknown people or companies, according to [Sophos]," writes WTOP's Max Smith. "They should be wary of confirmations for things they never booked. And computers also need to be up-to-date on security patches and anti-virus protection."