How do I fix this mile wide security hole?

[Chin Fang]

Every now and then I have to be away from my RS6000 console.  Up to now
I haven't found a good way to lock my console.  Xlock won't cut it since
anyone can walk up to my console, ALT-CNTL-BKSP, kills X, and then do 
whatever s/he wants!

I can do a really *dirty* kludge using a shell wrapper as follows:

xmodmap unbind CNTL
call xlock
[user passwd validation]
xmodmap rebind CNTL

However, I don't really think the above even qualifies as a "solution".
Up to now, I just log out completely to protect my account, a BIG hassle
indeed considering we have 9600! users in yp, and it takes more than 30s
to get passwd prompt after login prompt!

I confess that RS6000 is still new to me and I might have missed some
utilities that I could have taken advantage of.  If someone could
kindly point me to these or suggest me an elagent way to secure my console,
I would be very appreciative.

Please email your response.  I promise a summary if there is enough interest.

Regards,

Chin Fang
Mechanical Engineering Department
Stanford University
fangchin at leland.stanford.edu