If you don't want this to happen, one best way is to lock and protect your Chrome browser with a password so that no one else can access the internet without your permission. Take control over who access the internet through your browser; learn how to lock and protect your Chrome browser quickly and easily.
Browser Lock - Restrict People To Use Your Browser
Browser Lock is a free Google Chrome extension that disallows people to access the internet through your browser without your permission. If the plugin successfully installed, you can quickly lock your browser by simply pressing Ctrl+Shift+Lock keys.
For download and installation instructions, visit Browser Lock at Chrome App Store.
"How To Lock Mozilla Firefox With A Password" eHow tutorial.