Infect as many PCs as possible with miner

Hi guys, I know that mining with CPU is disadvantageous but I'm thinking to infect as many PCs as possible that are in my university. So we have this PCs at our availability and I was thinking to infect them all. So what's the legal risks? How can I do that in the fastest way possible? By doing so, can I make something or it's a waste of money? Let's consider that those PCs are pretty old