"People shouldn't be putting things in your computer without your consent," Leibowitz said, adding that the debate is moving to "not whether 'do not track' will exist but how it will be implemented."
Leibowitz said an FTC report calls for final implementation of a "do not track" mechanism and general privacy legislation that would cover issues such as data security, breach notification and regulation of data brokers.
The FTC chief said key industry leaders support the measures but that details need to be worked out.
Senator Jay Rockefeller, head of the Commerce Committee which held the hearing, said he hopes to bring privacy legislation up for a vote this year.
"Protecting consumer privacy is critical for all companies -- people need to trust the websites that they are visiting," Rockefeller told the hearing.