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(NECN/CNN) - It may surprise you to know that every time you log onto the internet... you're being watched. Companies track every website you visit and collect information on what you look at online. All this personal information makes up our "digital fingerprints."
Everyone who spends time on the internet has a digital fingerprint - a unique profile that is built by specialized companies.
"We actually don't really know who their clients are," said Peter Eckersley, Technologist of the Electronic Frontier Foundation, "So, they may be selling this technology to banks, they may be selling it to on-line advertising companies, and that's the bigger concern."
Eckersley says digital fingerprinting is a violation of every aspect of one's privacy.
"You should have the right to read what you want in private without someone looking over your shoulder reading along with you. As you pick up a magazine to read it, you don't want the magazine reading you."
Last March, Senator John Rockefeller introduced a bill to stop companies from tracking online movements - part of recommendations from the Federal Trade Commission. What it would require is internet browsers to have an option for users to select "do not track me". Eckersley says the technology already exists. All that is needed is congressional action.
"I think the scary thing is people don't understand what is out there about them, personally, that's linked the their online digital fingerprint." said Don Jackson, Director of Threat Intelligence for Secure Work.
Jackson says digital fingerprints are used for personalizing marketing and advertising campaigns and customized political messages. But, he says, there is also the danger they will be used with malicious intent.
"What we're doing is trusting these companies with the security of that information. We're entrusting them to guard that information, we don't want anybody to be able to break into the system and use it, but, unfortunately, when companies aggregate all that information in one spot, it makes them a target for hackers."
Security experts are concerned that there is no practical way to stop companies from using this technology. The best defense is to be aware that everything you do online is being watched.
Some more advice from Jackson: "Keep your anti-virus up to date, keep your computer up to date, but, for the most part, once the information leaves your computer, at least one person, that's the website that you are visiting, can track it."