Turns Out 90 Percent of the Internet’s Top Sites Leak Your Data to Third Parties
It’s no secret that websites typically send user data to third parties (typically without their knowledge or consent), but now new peer-reviewed research published by University of Pennsylvania privacy researcher and doctoral student Tim Libert shows that the scale of this is enormous “nine out of ten sites are leaking user data to an average of nine external domains.” That means that a single site you visit will send your data to nine outside websites.
Why should this concern you? Personal data is exactly what spear 
phishing uses to fool you into their trap. Spear phishing is a targeted email, using as much personal information about you to trick you into believing the email is safe. Clicking on a provided link usually downloads malware and gives hackers and cyber criminals privileged access to your computer. Perhaps this is worse than sharks!
“There is one web users sees in their browsers, but there is a much larger hidden web that is looking back at them,” according to Libert. “I always find it funny when old TV shows will have a gag where somebody on the screen can ‘see’ into your living room—it’s obviously silly with old technology, but that’s really how the web works! For every two eyes looking at a screen there are probably ten or more looking back at them.”
Libert cites Google as the worst culprit, but gives Twitter props for respecting browsers’ Do Not Track setting. He also points out that the NSA has leveraged commercial tracking tools in order to monitor users.
Using an anonymizing browser and protocol. such as Tor, is a way to ensure your privacy, as long as you don’t log into any personal accounts, such as Gmail and Facebook.
More details are available in this interesting article written by Brian Merchant, Senior Editor at Motherboard.com: http://motherboard.vice.com/en_uk/read/9-out-of-10-of-the-internets-top-websites-are-leaking-your-data