The Chinese Ministry of Industry and IT's announcement that all PCs sold in China must include government-approved filtering software is a profoundly worrying development for online privacy and free speech in that country. While the application, "Green Dam Youth Escort", claims to only block pornographic sites, the access to a home computer such filtering software requires means that it could also have the power to conduct all sorts of other surveillance and control — far more than China's current monitoring and blocking systems at the ISP level permits.

On present day operating systems, government-controlled software that are granted such admin rights would be able to collect IM and email conversations, install keyloggers, relay microphone and webcam recordings. It could prevent or detect the use of web proxies (the primary method of Chinese citizens seeking an uncensored Internet), and scan for privacy-protecting software like Tor and PGP. Business users of Chinese PCs will be vulnerable to state-sponsored corporate espionage. Foreign users of computers in China will be unable to guarantee the security of their communications.

Are these realistic threats? Absolutely: indeed, we've already seen what many suspect is the Chinese government's use of software in this way. A localised Chinese version of Skype included backdoors that passed on private IM conversations to third-parties. Tibetan dissidents have struggled with keylogging spyware that is uniquely targetted to this political group.

But until now, such software has relied on duping its users as to its function or on the poor security of their operating systems. "Green Dam Youth Escort" will allow the Chinese state an automatic foothold on every Chinese PC, installing their own code remotely through automatic upgrades.

PC distributors have already reacted negatively to the announcement, not least because of its unrealistic deadline of July 1st. Dell has said that it will only consider installing the software if its only purpose is to block pornographic content from children, and only if it can be disabled.

These companies need to continue the pushback, not just for reasons or practicality, or for privacy and surveillance, but in defence of their users' right to manage their own property.

Other software companies, like the anti-virus companies, can assist by detecting and removing such programs in just the same way as they defeat other malware that undermines user control (if they do not, they risk having criminal non-government malware use the Chinese program as method to conceal their own intentions, as happened with the Sony Rootkit).

Finally, Western governments need to understand that their own plans to infect computers with such software — under the proposed Loppsi 2 law in France, or the Federal Trojan project in Germany, or via the FBI's current domestic spyware projects — needs detailed scrutiny and firm judicial controls in place. The modern PC is as private and personal a locale as a citizen's home. Any state that claims to respect human rights and civil liberties should respect that privacy.