VPN services blocked in China as Astrill warns of 'increased censorship' following WW2 parade

A popular service used to bypass Chinese internet restrictions has told users it is facing "increased censorship" in the wake of a major military parade in Beijing.

On Monday, virtual private network (VPN) provider Astrill sent a message to users of its iPhone app, informing them that the Great Firewall was blocking all VPN protocols "using machine learning".

VPNs allow users to tunnel their internet traffic through an uncensored server, bypassing domestic restrictions or filtering.

Astrill had previously said that it was suffering service outages in the run up to the September 3 parade to mark the 70th anniversary of the end of the second world war.

The company did not respond to a request for comment.

"Due to upcoming Beijing's military parade next week, China is cracking down on IPSec VPNs using GFW auto-learning technique," Astrill said late last month.

That crackdown has now expanded to take in the widely used PPTP and L2TP protocols, according to the company's most recent statement.

"The authorities are hellbent on cracking down on circumvention tools, denying Chinese the ability to view uncensored overseas website," said Charlie Smith, founder of GreatFire.org, which monitors online censorship in China.

"We expect that the authorities will continue to take steps to shut down all circumvention tools and VPNs."

Smith warned that many corporate VPNs, which allow users to access secure email servers among other functions, may also be effected by the crackdown.

"Many companies, especially small-and-medium sized enterprises, [may] find that it is impossible to use the internet for simple and mundane everyday business tasks."

In August, two Chinese developers of anti-censorship apps removed their software from open-source code repository GitHub after alleged police pressure.

There has been a general increase in censorship and blocking of websites and anti-filtering services since the beginning of this year, according to GreatFire. In January, many popular VPN services were disrupted by what the People's Daily, the official mouthpiece of the Chinese Communist Party, described as an "upgrade for cyberspace sovereignty".

Last month, experts said that the White House should threaten the Great Firewall to drive home its concerns over alleged Chinese cyber espionage activities.