They can also be sued by the new employer for failing to give vital information about a reference. It is best to be honest and answer any questions asked about the former employee. I would not volunteer they were fired but would truthfully answer why they left our employ, if asked.
"I was there such a short time and it really wasn't pertinent to this position."
More than half of my career isn't on my resume. I'm old, and jobs I held twenty years ago generally aren't pertinent. I started a new job and said something about something I did a long time ago and my new boss said "that wasn't on your resume" "Yeah, if everything I did was on my resume it would be a small novel, not three pages."
Another trick - have him set up a small freelance IT business. Fixing people's computers, small business IT support, or something - it will give him something on his resume that will look like he's been doing something industry pertinent in the meantime.