Mac Security

I have a MacBook Air running OS X 10.8.3 and the Apple Genius tells me it has the
tightest security settings, BUT, I use my Mac to do in-class presentations (PDF docs)
and, after class, the prompt in the terminal window changes from Mackintosh-4 etc.
to Justins-Ipad. Am I being hacked?

Welcome to Mac-Forums.

Just based on the name of the machine changing (ignoring how it's happening) you are not beng hacked or anything remotely like that..

If you close the Terminal and re-open it, does the name revert back to what it should be?

Your not being hacked. If your worried about a virus you can download clam xav. There is not a virus for OS X as of now though so it won't do much good.

Security

Thanks for the reassurance!

Once the odd prompt appeared restarting the Mac or restarting the terminal
window didn't make it go away. When I changed my Mac password,
then it went away. BTW, my flash (hard) drive is fully encrypted.

I have some pretty savvy students and I'm concerned that they can download
my exam questions etc.

Many thanks,
elProf.

That does sound like one of your students -- named Justin -- worked out your old password.