A circumventor is a means by which blocking policies are "gone around". Oftentimes, blocking policies are implemented with proxy servers, and circumventors themselves are also proxy servers. A circumventor is a website page; it encounters a blocked site and "goes around it" or circumvents it by directing it to an unblocked site, so that the user can then view the blocked material. For example, circumventor elgooG was a way in which China's users could use Google after it had been blocked in that country. This particular type of circumventor, though, goes around only one block, while most circumventors unblock more than one site.
A circumventor can also let unauthorized people such as children or students access sites blocked to them, such as pornography, social networking, messaging programs, and so on. In fact, they are relatively sophisticated such that even as filters are implemented to block unauthorized people from accessing these sites, circumventors pop up that will allow them to go around the blocking software. In some cases, nonetheless, the filter can still intercept traffic going to the circumventor so that administrators can see what unauthorized users are visiting, even if they can actually access them when they shouldn't be.
Adults and other people who have been blocked from a particular website can also use a circumventor to see this material.
Circumventors can also be used to access material that is country-specific. This lets people from other countries use that information. For example, some webcasts and other types of media are restricted by country, and circumventors let other countries see this information even though it's been blocked.
Using circumventors is usually pretty safe, except for some circumventor sites run by third parties that can't be trusted. These sites have intentions to steal personal information, which of course makes them unsafe. Therefore, a good policy to have is that you shouldn't run personal information such as passwords or credit card numbers through a website that's been circumvented, just to be safe.
In addition, most schools and other office spaces restrict the online services and websites they use to their particular population. Circumventors do bypass censors in computers, but many sites that have been blocked by these organizations are deemed frivolous, such as social networking sites.
Proxy Web servers have become more sophisticated so that users can encrypt data or links coming from or going to other Web servers. This means that users can access websites that have been blocked previously.
One type of web proxy is called a CGI Proxy. These websites let users access a particular site through them. They are used in CGI or PHP format so that proxy functionality is more easily implemented. These proxies can allow access to websites that schools or corporations have blocked. They also usually hide a user's IP address from the websites they access, so that they have some anonymity attached to them.
Anonymous proxy servers can be a risk to those using them because any data being sent has to pass through the proxy server before it goes to the service, usually unencrypted. Therefore, if a particular service has a malicious intent, your personal information or credit card data, for example, can be captured by these services and therefore put you at risk for identity theft or worse.
In addition, because proxies often don't give personal information about the user, oftentimes, activities or the origins can be hidden. That said, intermediate proxy "hops" often do contain traces of information that can eventually lead back to the user him- or herself. Therefore, it behooves one to know what proxies are being used on your site.
In short, you should be very careful if you use proxy servers and only use those that you know have integrity, where you know the administrator can be known and trusted. Never use proxy servers you're not sure of. If you must use a proxy server you're not sure of, never submit personal information such as passwords or credit card numbers through it.
Because of proxy risks, you may find yourself being blocked from sites just as a matter of course, but this is more an inconvenience than an actual risk. Be aware of proxy risks and use circumventors wisely.
Andrew Green is part of the team behind A-Z Proxies an attempt to list from A to Z all web proxies. Andy has been actively working in the web proxy field since 2005 and has built up a wealth of knowledge on the subject.
