Bad update (infected?!)?

I had a little window pop up telling me there was a 'MacBook Pro EFI Firmware Update' available so I clicked 'Install and Restart'. It installed but in the process of restarting, it ejected the DVD I had in and also made a loud, short noise that didn't sound too healthy... after about a minute of loading, it switched on again.

Should I be worried or will this be a genuine update?

Thanks!

It's normal. A firmware update is different from a software update in that it updates the "brain" of your Mac. That's why you're warned about not installing firmware updates while on battery.