Online Ponzi schemes known as high-yield investment programs (HYIPs) that claim to offer returns of up to 100 percent or more -- per day -- are a growing threat to investors, the Financial Industry Regulatory Authority warned this week.

HYIPs (or "hippees") are unregistered investments that are peddled by con artists who create sophisticated websites to trick investors, according to FINRA. The scammers behind HYIPs are experts at using social media, using popular websites such as YouTube, Twitter and Facebook to create the illusion that people you know believe these “investments” are legitimate.

The Federal Bureau of Investigation said that the number of new HYIP investigations opened in fiscal 2009 more than doubled from the sale period a year earlier. One such scheme, known as Pathway to Prosperity — better known as the Pathway to Poverty scheme -- allegedly defrauded more than 40,000 investors in over 120 countries for a total loss of $70 million, FINRA said.

"HYIPs are old-fashioned Ponzi schemes dressed up for a Web 2.0 world. Some of these schemes encourage people to bring in new victims, while others entice investors to 'ride the Ponzi' by attempting to get in and get out before the scheme collapses," said FINRA Senior Vice President John Gannon.

HYIPs typically promise extraordinarily high returns, FINRA said. A scam called the Genius Fund at one time promised a return of up to 40 percent a day, or 106 percent over two days. Victims are encouraged to aid in the scheme through "referral bonuses" of up to 25 percent.

You can find more information about HYIPs, steps you can take to protect yourself against fraud, and a resource for investors who think they’ve been scammed at FINRA’s website.