Public Computer management systems

I have seen ads for systems that will allow a library to
load software
and controls on a central server and the system will handle
all the
computers within the network, providing security, internet
access with
whatever limits the administrator chooses, and selected
software,
without allowing anything to be loaded onto the individual
PCs.  But of
course, now that I am looking for information about such a
system I'm
not able to find anything. 

Are any of you out there using this sort of system?  If so,
which one?
What are the ups and downs of it?

Thanks for your help!!
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