Millions of people snatched up legitimate Cyber Monday deals, but the federal government is advising caution. Some online purchases are actually "knockoff" purses and clothing. Other counterfeit items sold online can be downright dangerous.
Federal agents are trying to put counterfeit sites out of business. On Monday, the federal government shut down 150 website domains, an 80 percent increase over last year's Cyber Monday.
For consumers, Cyber Monday is the time to hit the Internet for holiday shopping deals. But to federal agents, Monday is significant in another way.
"'Intellectual property rights Monday'," said Claude Arnold, Special Agent in Charge, U.S. Immigration Customs and Enforcement.
With the growing problem of knockoffs being sold online, not only are shoppers missing out on quality, they could also be unwittingly aiding international criminal organizations linked to more serious crimes.
And in some cases, it's not only illegal, it's dangerous.
"Not only are they substandard, but you don't know what's in these products," said Arnold. "You don't know what's in these counterfeit Viagra pills, chemically. They're not regulated."
Pharmaceuticals are at the forefront of the online counterfeit industry. Other big sellers include counterfeit batteries that can leak acid, Christmas lights that can cause fires, and of course electronics, handbags and movies.
So how do you know what you're getting?
"If the price is too good to be true, it is too good to be true," said Arnold. "If something is 50 percent less than what the retail price would be, then it's probably counterfeit."
Since June 2010, the government has shut down 350 domain names, with a notification posted along with a public-service announcement about why sites were taken offline.
The most obvious indicator when dealing with counterfeit merchandise is the quality of the product. When dealing with items online, the quality of the website is sometimes an indicator. If there's no contact information on the site, that's another red flag.