glype proxy application is installed on many random sites to provide a portal to unfiltered internet access. Here is one as an example: "https://www.plypan.com/admin+++/index.php?e=no_hotlink" It is easy to find these in google by searching for the phrase "powered by glype".

When auto categorizing sites, if you were to set the script to run a site search on google for that domain for the phrase "powered by glype" if it returned a result the site should get the categorization: "Proxy & Filter Avoidance" added to it.

There may be a more elegant solution for detecting the presence of the glype script on a domain that you guys could figure out.

If a solution for this isn't found your system will forever be easily bypassible as new glype installs pop up all the time in google search results and the category given is usually "information technology".