First, you never know which sites and downloads are safe. While good anti-virus software is able to block infected downloads, it does not label results in major search engines (Google, Bing, Yahoo) or social media.
avast! Free Antivirus does have the WebRep module, but it is quite new and many sites are still uncategorized.
Protections built into web browsers (SmartScreen Filter, Google Safe Browsing) also fail quite often.
- WOT Safe Surfing Tool is a free browser add-on that works with Apple Safari, Google Chrome, Microsoft Internet Explorer, Mozilla Firefox and Opera. Use this one as an extra safety feature while browsing the web.
Second, you really-really must keep all programs up to date. Most threats today misuse outdated and insecure programs for spreading spyware, banking trojans and other dangerous malware. All it takes is opening an infected web page and your Windows PC is a member of botnet.
- Free Secunia Personal Software Inspector (aka PSI) updates most important programs automatically, without any effort from you. Really, it's dead simple to use.
- Double-check Windows Update settings and verify you have Microsoft Update turned on. The latter provides automatic updates to all installed Microsoft programs, not just Windows. If you encounter problems using Windows Update, read the Reinstall Windows Update tutorial.
Third, online banking is so widespread that cybercrooks invent jaw-dropping techniques to steal your money. Some can even bypass smart card and two-factor authentication to display a forged page in your web browser. And then there's the "good old" phishing - stealing user names and passwords via web pages that try to fake authentic services (from Twitter, Facebook and Craigslist to iTunes, Amazon and banks).
- Free Trusteer Rapport works in Chrome, Firefox, Internet Explorer and Safari. It provides the best protection against banking malware (and it is capable of removing them!) and phishing.
Fourth, no software is bullet-proof. Even when you patch programs quickly (or use Windows Update and Secunia PSI to do the job for you) after an update has been released, there can still be undisclosed security bugs, often called zero-day threats.
- Free Microsoft EMET (Enhanced Mitigation Experience Toolkit) is capable of enforcing special memory protection techniques to provide protection from zero-day security bugs. It may sound way too technical, but the actual configuration process is quite simple - just add a program and select which protections to use.