The Chinese government has backed away from mandating filtering software on all personal computers in China, in a move that averts a dangerous escalation in its censorship powers.

But however controversial and unworkable China's plan to require Internet filters on PCs proved to be, Western firms have largely themselves to blame for creating and selling such filters in the first place.

The danger rears its head whenever technology created to solve some specific security problem is put to new and unintended use, not just in repressive regimes like China, Iran or Saudi Arabia, but professed freedom-loving countries in Europe or the USA.

What is good and what is evil? asks Mikko Hypponen, chief research officer at Finnish anti-virus software company F-Secure Corp. It is really a very basic problem that security people face.

A computer password cracker in the wrong hands is considered malicious, of course. But corporate network administrators rely on the same tools to recover lost documents when employees forget computer passwords. Voice recognition software used in corporate call centres to automate and improve customer service can be used by police to wiretap suspects on a grand scale.

On Tuesday, China's official news agency reported that a government ministry had abruptly backed down from requiring that every PC sold in China include a censorship program called Green Dam-Youth Escort.

The software blocks web sites using a blacklist of keywords judged to be sexual or politically sensitive, or flesh-coloured images it assumes are naked bodies. But University of Michigan researchers found that the software developed by a Chinese firm had liberally borrowed the code of parental control software CyberSitter from the California-based firm Solid Oak.

Mobile network maker Nokia Siemens Networks was criticized last month after the Iran election protests for supplying deep packet inspection technology to mobile phone companies which Iran's government allegedly used to track online dissidents. The same software for so-called lawful intercepts is widely used in phone networks around the world, be it Iran, China or the United States. The main differences are only how far network monitoring goes and to what uses such information is put.

These issues cannot be dismissed merely as unauthorized uses by bad cops in foreign lands. All the world's biggest technology suppliers play some role in creating security tools that have Janus-like qualities, depending on the intentions of their users.

The dark side of the Internet is not some isolated corner. It is built with the same tools good guys use with the best of intentions, without considering their Orwellian surveillance potential. It is just the dual use of networked, interconnected technologies.

Companies such as IBM, Cisco, Intel and Dell are some of the dozens of vendors that market remote data recovery tools to police agencies that can be used to remotely monitor suspects. Once available commercially, it's only a matter of time before such software is sold or copied for use by authorities in repressive regimes.

Canada's Absolute Software sells such software for network administrators to track the location and use of all corporate laptops or Blackberries used in their organizations. If a computer is lost or stolen, it can be told to phone the factory every 15 minutes. Absolute then turns over the Internet address of the machine to police to recover the device. In countries with fewer safeguards, such tools can be used to snoop on or prosecute political dissidents.

Hypponen says computers have raised a host of issues that hardly existed in the Cold War era. Monitoring traditional mail can be done, but takes a lot of manpower, he says. E-mail monitoring can be done which takes very little manpower.

The very openness of the Internet has created a vast market for security tools used for Web filtering, network monitoring and text or video surveillance.

The power of technology to do good needs to be weighed against its powers to do evil. The many positive tasks computers perform for us need to be set against their growing powers as surveillance tools and mechanisms of repression. Just because a technology can be built, doesn't mean it should be. As consumers, we need to be careful what we wish for in the way of modern conveniences.

- At the time of publication Eric Auchard did not own any direct investments in securities mentioned in this article. He may be an owner indirectly as an investor in a fund. -

(Editing by Martin Langfield)