SonicWALL Filters Harmless Sites
It is the right of private companies to block access to certain sites for their employees or customers, certainly. But in the United States, some customers of Panera Bread, a popular nationwide chain restaurant that offers free wifi, are frustrated. It seems that Panera practices what is popularly known as overblocking: the unintentional filtering of harmless web sites.
One such harmless site is http://tinyurl.com, which SonicWALL classifies doubly: As "Category 27: Information Technology/Computers" and "Category 28: Hacking/Proxy Avoidance Systems" (see image). While the former is certainly correct, the latter is questionable. Tinyurl is not a proxy, rather, it is simply used to shorten URLs, which are then re-directed. In theory, if a tinyurl were used to re-direct to a filtered site, the site would still not be visible.
Tinyurl is particularly popular with users of micro-blogging service Twitter; most Twitter applications automatically turn long URLs into tinyurls. Therefore, SonicWALL's filtering of tinyurl renders Twitter nearly useless.
Tinyurl is not the only case of overblocking by SonicWALL. Popular comic xkcd is known to be blocked in businesses using SonicWALL filters as well.