Ask HN: What's with this "Your IP is infected" junk?

okay HN, I'm noticing something more and more. My university uplink must have been tagged by something because more and more, I'm seeing a "your IP has been flagged as infected" messages on some pages off HN. Scanning with SheildsUp shows... nothing. Upon talking to my schools IT dept -- and apparently the ISP they use has also tagged them. So what's the tech? Should I be concerned? What's TRWTF?