urllstck.exe is a part of the Norton Internet Security Suite, and is responsible for real-time checking of URL's during your browsing experience. This program is important for the stable and secure running of your computer and should not be terminated.
Non-system processes like urllstck.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that your registry has suffered fragmentation and accumulated invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues