The #1 most important thing you can do to protect your computer from malware and malicious actors is to regularly patch everything. 90-95% of Microsoft's and Apple's OS patches are to fix security problems. Having patched software is even more important than having a good anti-virus installed. If you're on Windows, have your Windows Updater run and auto-install updates at least once a week, preferably at night so it doesn't interrupt whatever you're doing when you're surfing, paying bills, etc. In addition, there is a *free* aftermarket tool called "Secunia PSI" that will send you alerts when other pieces of software (like Chrome, Firefox, Adobe products, etc). Secunia can even be configured to auto-update those things which are not auto-updated by Windows Update. There are network scanning tools (I use one called Nexpose) that will tell me which patches a computer is missing. If I were a bad guy, I'd use this info to know precisely how to attack you. Since I'm a good guy, I use it to tell my IT operations people what patches they need to be deploying to our corporate environment, and to prioritize all of this by the comparative risk of a given vulnerability.