BEIJING (Reuters) - Internet services that allow people to freely access blocked websites and apps from within China have seen more severe disruptions this week, said three providers, moves that Chinese state media said were justified.
The services affected include popular Virtual Private Network (VPN) providers Astrill, StrongVPN and Golden Frog, which are engaged in a technological arms race to one-up China's highly sophisticated Great Firewall internet censorship system.
"This week's attack on VPNs that affected us and other VPN providers is more sophisticated than what we've seen in the past," said Sunday Yokubaitis, president of Golden Frog.
Chinese internet analysts said internet services should observe the network governance of the country "for safety," according to the Global Times, an influential tabloid published by the ruling Communist Party's official People's Daily newspaper.
A cyber security expert at a government-backed Chinese think-tank told the Global Times that China's Great Firewall "has been upgraded for cyberspace sovereignty", in a rare acknowledgement in state-run media of the country's efforts to block technical workarounds to the firewall.
Attacks and blocks on foreign internet services have become increasingly common in China. Censors maintain a tight grip on what can and cannot be published online to eliminate anything seen as a threat to the ruling Communist Party.
VPNs allow individuals and companies to access websites and services that are normally blocked in China, including those operated by Google Inc, Facebook Inc and Twitter Inc.
Almost all foreign and many domestic companies in China use VPNs to conduct business relatively unimpeded by disruptions to web services. The services that have seen disruptions recently are widely used by individuals, largely affecting mobile devices.
A notice from Astrill this week said that certain VPN protocols are "blocked in almost real-time" in China.
StrongVPN said on its blog that some of its servers were not working for users in China. Golden Frog, which operates the service VyprVPN, also reported heightened disruptions in recent past days.
Hua Chunying, a spokeswoman for China's Foreign Ministry, said she had not seen reports related to the VPN disruptions and was not aware of the specifics.
Reporting by Paul Carsten, Megha Rajagopalan and Sui-Lee Wee; Editing by Nick Macfie