Applications that have reached the ends of their lives, are no longer maintained by their original developers, and do not receive security updates are a problem. However, many users forget to remove these applications from their machines or do not realize that they pose a danger.
"If a program is end-of-life, uninstall it," says Kasper Lindgaard, director of research and security at Secunia Research, which has compiled a list of the riskiest applications. "If you are no longer using a program, uninstall it so that you do not end up forgetting about it. If you leave it sitting in the background it may become outdated and unsecure."
In 2013, the number of end-of-life applications on user machines was between 3 and 4 percent, but it's hovered between 5 and 6 percent for the past 12 months.
According to a report Secunia released at the end of October, the following are the 10 riskiest applications, based on market share.