Industry groups have warned of counterfeit holiday light strands with faulty wiring that could be a fire hazard; problems with knockoff toys include unsafe lead levels and small parts that pose a choking risk. Analysis of counterfeit perfumes has found ingredients such as antifreeze and urine.  Read MoreShoppers may unknowingly buy stolen goods  In other words, not the kind of festive impression you're hoping to make.  If there's good news, it's that fewer consumers are purposely hunting for fakes to save a buck. MarkMonitor estimates there's one person actually looking for that knockoff for every 28 bargain hunters. That's down from one for every 20 bargain hunters in 2012.  "Still, it's a very big problem," said Frederick Felman, chief marketing officer for MarkMonitor. Especially as the ranks of online shoppers swell—this year, the National Retail Federation expects online sales growth of up to 11 percent, versus 4.1 percent in overall sales growth. "There are going to be a lot of new shoppers there who will be readily duped by this," he said.  Read More Alibaba, Amazon and eBay fight counterfeiters  Avoiding fakes isn't easy. "The question presumes you can tell," Dworsky said. Even if you do know all the hallmarks of, say, a particular designer bag when buying online, it's easy for a counterfeit seller to send something other than what's pictured or described.  Scrutinizing the retailer helps. Some brands, including Apple and Coach, also post lists on their websites of retailers authorized to sell or distribute their products.  Read MoreKeeping an eye out for hidden holiday expenses  If a web search turns up a store you aren't familiar with, search for the name in conjunction with terms like "counterfeit" or "scam" to see if that's an issue, Feldman said. "You want to look at the reviews, which will tell you the quality of the experience people have," he said. That holds true even on big-name retailers like Amazon or eBay, where third-party sellers can create their own product listings.  Of course, the biggest red flag is price. "If the price is just so out of line for the going price of an item, it has to raise an eyebrow," said Dworsky.  Paying with a credit card is smart, too. The Fair Credit Billing Act gives cardholders the right to dispute transactions, said Dworsky. "That's going to be your ultimate protection," he said.
One in 10 bargain hunters ends up on a counterfeit seller's website, according to a new report. How to ensure you're getting the best (real) deal.