Quick question about 'ps'
 

Is there are way to make it so that when a user issues command "ps aux," it is automatically rewritten as "ps ux?" That is, a way to make it so no user can pass the 'a' argument to ps?

Look into using "aliases".

I think the problem isn't solved

Mr.reddazz do u mean aliasing it in /etc/profile

what if the user over alias it

all u have to do is modify the source code and recompile it

Yeah thats what I meant, but I am not sure what will happen if the user aliases in their .bash_profile.

If you only want users to see their own processes, there are security patches to the kernel that do that - I know www.openwall.com's patch will do that for a 2.4 series kernel.