China's Great Wall is quite popular, but there is another wall quite more impressive and impacting on the locals' lives: the Great (Virtual) Wall of Censorship, which affects the Internet world with a special focus. Inside China it can be hard to access some of the most popular sites worldwide, causing for people to find tools to circumvent these limitations.
One of the most popular ways to do so is using VPNs. They are advancing discreetly in China, as a means of accessing sites banned by the government and, for now, these services are not being interfered with by the authorities.
Big sites, such as Facebook, Twitter, Gmail or YouTube, are blocked in China, through the use of a "firewall" spanning throughout the entire country that filters web traffic. With this, it prevents Chinese citizens from accessing foreign sites, sites that have something that might threaten the power of the Chinese Communist Party. Danny Levinson, editor of the site ChinaTechNews.com, commented on this matter:
"As long as the VPN operates outside mainland China, there should be no problem. We use our own VPN and it works well. They are like a small escape valve, but if the army of Chinese Internet uses start using them, there will probably be targeted by authorities."
Chinese authorities rarely block overseas-based VPNs, and is not likely that they ever interfere with them if the number of users remains small. Still, the government acts aggressively against the free proxy servers, which are more common and can also be used to unblock forbidden sites. (Paid) foreign VPNs have been blocked just once in the past, according to some citizen reports, but users still are able to choose the best VPN service.
Numbers from Wikipedia show that, last September, the number of websites blocked in mainland China (excluding Hong Kong and Macau) topped 3,000.