Facebook has come under fire in recent weeks over claims that the company violates users' privacy by publicizing too much of individual's personal information. The Federal Trade Commission has expressed concerns over what the company learns about individuals who use the website.

Sen. Jay Rockefeller (D-W.Va.), chairman of the Commerce, Science and Transportation Committee, announced Wednesday that he will be holding a hearing to investigate how Facebook tracks users online even after they've logged out, reported the L.A. Times.

No company should track customers without their knowledge or consent, especially a company with 800 million users and a trove of unique personal data on its users, Rockefeller said in a statement according to L.A. Times. If Facebook or any other company is falsely leading people to believe that they can log out of the site and not be tracked, that is alarming.

Facebook spokesman Andrew Noyes maintains that the company is not tracking information in the same way other ad-networks and websites do. He claims Facebook does not sell users' information to third parties and deletes or makes data anonymous after 90 days. Instead, he says Facebook uses cookies to keep accounts secure and personalize content based on Likes.

When someone logs off of Facebook, we delete certain cookies and reduce the amount of information we receive when the person visits websites that contain social plug-ins such as the Like button, he said in an emailed statement to the L.A. Times. We have made these practices clear in our Privacy Policy and Help Center since the launch of social plug-ins. We appreciate Sen. Rockefeller's interest in protecting consumer privacy and look forward to discussing this with him.

According to USA Today, Noyes says the company has no plans to change how we use this data. He also says the company's intentions stand in stark contrast to the many ad networks and data brokers that deliberately and, in many cases, surreptitiously track people to create profiles of their behavior, sell that content to the highest bidder, or use that content to target ads.

Facebook engineering director Arturo Bejar, however, disclosed details to USA Today of how Facebook uses tracking-cookie technology, which compiles a log of web pages users have visited in the past 90 days. He says that Facebook also keeps track of millions of non-members so long as they've visited a Facebook web page for any reason.

Bejar told USA Today that when users are logged into Facebook, the website inserts a browser cookie and a session cookie into their web browser. The session cookie then tracks the user's profile date (including name, email address, list of friends, user preferences from use of the like button), unique data (IP address, screen resolution, operating system, browser version) and time stamp (time, date, and each URL visited that uses a Facebook plug-in).

Bejar said even when users are logged out of Facebook, or if non-Facebook users visit the site for the first time, a browser identifier cookie is activated. The browser cookie then tracks and logs unique data, time stamp and an alphanumeric number, which is unique to the cookie.

Overall, Facebook tracks data to help boost security, like identifying and blocking fake accounts, scam, and viral links. Tracking data is also used to enhance user experience. According to Bejar, the logs help to improve the display and usability of Like buttons and other plug-in services on third-party websites. Finally, tracking data is used to generate ad revenue. Facebook claims not to use tracking logs to target ads to specific individuals; however, there are sponsored ads that appear on the Facebook website, which are directed to certain members based on self-disclosed information and preferences expressed by clicking Like buttons.

Congress is currently hashing out new guidelines for privacy online. Privacy advocates hope to limit the amount of information companies are allowed to collect from users, hoping that users can instead be in control of what information companies and ad networks could access and track whenever they go online.