Have you heard of online behavioral advertising?

That’s Web sites tracking your online activities, including your searches, and delivering advertising to you based on your interests. For now, the practice is unregulated by the federal government, and companies are supposed to regulate themselves.

But the government and privacy experts are scrutinizing this growing practice in light of privacy concerns. They say they worry most about use of sensitive information regarding finance, children’s privacy, health and Social Security numbers.

A Federal Trade Commission report says a company engaged in the practice must provide “clear and prominent notice” to consumers that it tracks Web habits to match related advertising. The report says such alerts are often posted in lengthy and difficult-to-understand notices.

Companies need to create effective disclosure statements separate from privacy policies, the report says. It also says companies should let consumers opt out of behavioral advertising.