Facebook denied it had spilled details of its users.
Facebook is also fighting a California privacy bill that would ensure social networking services to require users set up their privacy settings when they first register.
This week's Senate hearing will start at 10 a.m. ET. Sen. John Kerry (D-Mass.) chairs the subcommittee.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is firstname.lastname@example.org .
Read more about privacy in Computerworld's Privacy Topic Center.