The Securities and Exchange Commission said it has shut down ZeekRewards.com, a $600 million online Ponzi and pyramid scheme that was on the verge of collapse and had raised money from more than one million customers.

The SEC alleges online marketer Paul Burks of Lexington, N.C., and his company, Rex Venture Group, raised the money through the website ZeekRewards.com, which they began in January 2011.

Mr....