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Can Java Report my Personal Information?
 
If you are particularly serious about privacy, you may have visited an online privacy report website like that run by Privacy.net (http://privacy.net/analyze). These sites may report system information like your screen width and height, the date and time on your computer, and the amount of free memory on your computer. Although this may be surprising and make you feel violated, it is actually not as much of an intrusion as it appears.

These sites use Java or Javascript to run a small application on your computer. This application discovers the system information aforementioned, and displays it on the privacy site's web page. Although it may look like the privacy site knows your screen size and is displaying it on its page, the information actually stays on your computer. The small application displays this information directly on your computer, without sending it back to the privacy site. Because the application's output appears in the page, it looks like the page itself has this information. In actuality the page does not--the information is inserted into the page on your computer.

In general, Java and Javascript programs are executed in protected environments which are designed to protect your computer, your data and your information. These environments should block the transmission of information back to web sites, although they will allow this information to be displayed on your screen.