Windows runs many processes which may include various unknow viruses. Svchost.exe is one strange process in windows OS. You will find many instances of the process running under the same name. These processes consume a lot of memory and can not be terminated as they provide some necessary services like windows firewall, windows defender etc.
For such situations, you can use : Svchost Process Analyzer. It is a free tool that requires no installation and will add no entry to registry keys.