Browser plugins

 HTTPS Everywhere: Available for Firefox, Chrome, and Opera, HTTPS Everywhere is a plugin created by the Tor Project and Electronic Frontier Foundation (EFF) to expand HTTPS encryption to many websites, improving the security of your communication with them.

NoScript Security Suite: Endorsed by Edward Snowden as a means to combat government surveillance, this plugin has been built for Firefox and other Mozilla-based browsers for the purposes of disabling active content including JavaScript, which may be used to track your online activity. Users can also choose which domains to trust and whitelist.
Disconnect: Another worthy addition to the list, Disconnect provides a visual guide to websites that are tracking your activity. Invisible trackers that monitor you and may also expose you to malicious content can be blocked. Disconnect is available for Chrome, Firefox, Safari, and Opera.
Facebook Container: In a time where Facebook has come under fire for its data collection and sharing practices time after time, Mozilla's Facebook Container application is a worthwhile plugin to download if you are worried about the social media network tracking your visits to other websites. The plugin isolates your Facebook profile and creates a form of browser-based container to prevent third-party advertisers and Facebook tracking outside of the network. While not bulletproof, this add-on is worth considering if you want to separate Facebook from the rest of your browsing activities.
Privacy Badger: Last but certainly not least, the EFF's Opera, Firefox, and Chrome-supporting plugin Privacy Badger is focused on preventing ad networks from tracking you. The software monitors third parties that attempt to track users through cookies and digital fingerprinting and will automatically block those which use multiple tracking techniques. The plugin also includes color-coded indicators of domain tracking scripts.
You should also monitor your extensions and plugins lists. Check them often to make sure there is nothing installed you were previously unaware of -- any suspicious software could be a sign of a malware infection.
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