U.S. homes were in foreclosure in February than in any month since December 2006, RealtyTrac reported Thursday. 21 percent of homes now in foreclosure are "zombie properties" abandoned by their owners, the housing data reporting service said. In some cities, one-third of foreclosed homes are abandoned. "Cold weather and a short month certainly contributed to a seasonal drop in foreclosure activity in February, but the reality is that new activity is no longer the biggest threat to the housing market when it comes to foreclosures," said Daren Blomquist, vice president at RealtyTrac. "The biggest threat from foreclosures going forward is properties that have been lingering in the foreclosure process for years, many of them vacant with neither the distressed homeowner or the foreclosing lender taking responsibility for maintenance and upkeep of the home -- or at the very least facilitating a sale to a new homeowner more likely to perform needed upkeep and maintenance. RealtyTrac in its monthly U.S. Foreclosure Report said there were filings on 112,498 properties in February, including new filings, notices of auctions and other legal action. That was down 10 percent decrease from January and 27 percent from February 2013. Copyright 2014 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.