As previously announced by Microsoft, support for older versions of Internet Explorer has ended. Windows 7 users should make sure they have installed Internet Explorer ver. 11, and should not be using any older versions of Internet Explorer. When support is stopped for a browser or operating system, there are no new security patches, and malware may attempt to use newly-discovered vulnerabilities in the unsupported software.
If you are still using Windows XP (for which support ended April 2014) or Windows Server 2003 (support ended July 2015), this is another reason why you should upgrade or replace with a current supported operating system. Neither of these unsupported operating systems will run Internet Explorer 11. As a temporary workaround, you might want to use an alternate browser, such as Chrome or Firefox, but remember the underlying operating system is not supported and is much more vulnerable to malware.
If you are running the original version of Windows 8, you are also vulnerable with an unsupported operating system. First upgrade to Windows 8.1, and then strongly consider further upgrading to Windows 10. In addition to getting a current supported operating system, most agree that Microsoft made Windows 8.1, and especially Windows 10, easier to user on desktop and laptop PCs. Many businesses running Windows 7 are not upgrading to Windows 10 at this time, as Windows 7 Professional SP1 Extended Support (security updates) runs until January 2020.
All users should make sure that they are set to download current Microsoft security updates and patches. As noted, that is NOT available for unsupported operating systems and browsers.
For more information on the Microsoft Support Lifecycle, see: https://support.microsoft.com/en-us/lifecycle