Overview
Network printers on campus are occasionally printing out sheets of paper with text similar to below:
GET http://www.baidu.com/ HTTP/1.1 Host: www.baidu.com Accept: */* Pragma: no-cache User-Agent:
It is caused by a web probe that hits port 9100 at the printer's network address. Printers appear to these scans as a possible proxy. The printed pages are the commands sent as a test of possible proxies for use. The printer interprets the request as a print job and prints out the given command. The issue can be reproduced by visiting the IP or hostname of any printer on port 9100. All printer makes and models seem to be affected.
Resolution
There are a few possible options for preventing this but the most comprehensive ones require changes to the network infrastructure. For some models, like the Konica Minolta copiers, you can block these proxy requests with IP filtering. Instructions for the KM copiers are available here.