Heimdal Free is a program that scans your computer for outdated and possibly vulnerable programs and automatically updates them to the latest version for you. One of the most common vectors that malware use to infect your computer are vulnerabilities found in outdated 3rd party programs installed on your computer. Using a vulnerable software scanner like Heimdal allows these programs to automatically be updated when a new version is released. This allows your computer to run more securely as your 3rd party programs will no longer be vulnerable to a variety of exploit kit attacks found on the web
Secunia PSI is a tool that can be used to monitor your installed applications for new updates. When started, Secunia PSI will scan your computer for applications and install any updates that are available for them. This allows your computer to remain secure from possible vulnerabilities in your installed programs.