Note: This article was originally posted in 2008, but has been updated with new information.

Every IT professional has (or should have) a software toolkit that makes troubleshooting, analyzing, and diagnosing an infected machine easier. Even better? Install programs that help prevent infection in the first place. What’s even better than that? If you don’t mind installing products from several different developers, you can build an entire security suite without spending a penny! Following are a few of my favorite programs that help prevent and/or remove infection:

AVG Anti-Virus Free Edition

AVG Technologies (formerly Grisoft) has been offering this free anti-virus product for years. The latest iteration, version 18, adds basic protection against viruses, spyware, ransomware and identity theft. This is not a comprehensive security product as the paid version is, but when used in concert with other free security products listed on this page it forms an important building block for a free security suite.

Comodo Firewall Pro

If you decide the built-in firewall that Windows offers is not enough protection, then turn to the excellent Comodo Firewall and CIS. It offers a hardened browser, sandboxing, and secure DNS lookup. It’s also easy to use, as it comes preconfigured for nearly a million programs. Keep an eye out as you install it, however, as you might end up changing your default browser, home page, and search engine if you don’t careful scrutinize the the screens and popups that occur during installation.

Spybot Search and Destroy

This venerable program has become a staple in the anti-malware/anti-spyware protection arena. It provides detection and protection, meaning that you can install it on a machine that is suspected of infection and use it to detect and remove malignant programs, and then leave it installed to protect against future infection attempts. For users with older versions of Windows, prior versions of S&D are still available at the site.

McAfee WebAdvisor

WebAdvisor (previously SiteAdvisor) is a free plug-in for Internet Explorer 9 or higher, or the latest versions of Firefox and Chrome, that helps you stay safe while you surf the Internet by scanning downloads and ensuring you type URLs correctly. It helps keep you secure from adware, spam, and phishing (on-line scams). It is supported on Windows 7, Windows 8/8.1, and Windows 10.

Flexera Personal Software Inspector

Regardless of what security programs are installed, no system is safe if its applications contain vulnerabilities. Flexera (previously Secunia) PSI scans your computer for you and determines if any of your installed software need security updates or patches. Thousands of applications are monitored, so you can use the product with confidence.

Panda Anti-Rootkit

Rootkits can be malicious programs used to access, monitor, or control a machine without the owner being aware. Panda’s free software helps to detect and remove rootkits from your system. Please read PC Magazine’s review for more information.

Malwarebytes Personal Edition Free

Of all the programs discussed on this page, Malwarebytes is probably the best tool for remediation of an infected machine. The free version will scan a machine and remove malware and viruses, but only the paid version offers protection. That’s an important distinction, because it would be easy to install it and assume it’s going to keep you safe, especially if you opt for the 14-day trial of the full version of the software. So the free version is an excellent tool to run if you suspect your system has an issue that another security product failed to detect. But if you want ongoing protection, you will need to use another security product (such as the built-in Windows Defender or the AVG Antivirus Free discussed at the top of this page) or invest in the Premium version of Malwarebytes.