svchost.exe .. what?

When I bring up my task manager and look under Processes, I find at least 6 svchost.exe running under SYSTEM, LOCAL SERVICE and NETWORK SERVICE. One of the system ones is eating up about 30,000k of mem. the others are chewing up about 4,000k each. What are these and how can I stop them from multiplying?

Also there is something called MASSrv.exe thats eating 40,000k

svchost is normal: http://support.microsoft.com/kb/314056/en-us
30M is excessive though.

massrv is McAfee. Get rid of it.