As the surreptitious tracking of Internet users becomes more aggressive and widespread, tiny start-ups and technology giants alike are pushing a new product: privacy.

Companies including Microsoft Corp., McAfee Inc.—and even some online-tracking companies themselves—are rolling out new ways to protect users from having their movements monitored online. Some are going further and starting to pay people a commission every time their personal details are used by marketing companies.

“Data is a new form of currency,” says Shane Green, chief executive of a Washington start-up, Personal Inc, which has raised $7.6 million for a business that aims to help people profit from providing their personal information to advertisers. More>>