My university blocks access to sci-hub on the claim that it has previously hosted malware. Apparently it attempted to infiltrate the visiting computer and act as a proxy server and/or grab the user's institutional login credentials, in order to access otherwise pay walled literature. At least, that's what I was told when I complained it was blocked.

Fortunately, they left libgen (http://gen.lib.rus.ec/) unblocked - as they weren't concerned about copyright issues, only malware threats - which has an entire searchable mirror of all papers and books downloaded via sci-hub. It's a fantastic, incredibly useful resource and I hope it continues to operate unscathed.