Researchers at security firm Finjan have discovered details of a new type of banking Trojan horse that doesn't just steal your bank log-in credentials but actually steals money from your account while you are logged in and displays a fake balance.

The bank Trojan, dubbed URLZone, has features designed to thwart fraud detection systems which are triggered by unusual transactions, Yuval Ben-Itzhak, chief technology officer at Finjan, said in an interview Tuesday. For instance, the software is...