Complicating its efforts to accelerate advertising revenue, Facebook has agreed to make it clear to users that when they click to like a product on Facebook, their names and photos can be used to plug the product. They will also be given a chance to decline the opportunity to be unpaid endorsers.

The changes are part of a settlement for a class-action lawsuit against Facebook in Federal District Court in California. The agreement compels the company to change one of its most effective advertising tools, known as Sponsored Stories.

According to the agreement, filed Wednesday with the court in San Jose, Facebook users will be able to control and see which of their actions on Facebook are used to generate advertisements seen by their Facebook friends. For Facebook users under 18, there is an additional requirement: the company must give parents the opportunity to keep their children out of advertisements.

Until now, Facebook users were unaware when and how they were exploited for advertising, and they may not have realized that a click on something as vague as a like button could be used to enrich Facebook, the company.

The changes are to be made within the next six months. How many Facebook users will decline to participate in the ads remains to be seen. An economist hired by the plaintiffs’ lawyers, Fernando Torres, testified that giving users such a choice could cost Facebook $103 million in advertising revenue.