really
smss is a windows session manager...
csrss is dll subsection manager...
if you want, load up a command prompt, and type:
tasklist /svc
it'll show you every dll hook attached to csrss...
if you want more info, look on the microsoft site
smss CAN be exploited by common trojans, but it's also a default service in winxp....
(take a look at your process manager, you'll probably see it there too.....)