In the annals of the net, one of the sacred texts is John Gilmore's aphorism that "the internet interprets censorship as damage and routes around it". Mr Gilmore is a celebrated engineer, entrepreneur and libertarian activist, who is regarded by the US Department of Homeland Security, the National Security Agency and men in suits everywhere as a pain in the ass. He was the fifth employee of Sun Microsystems, which meant that he made a lot of money early in life, and he has devoted the rest of his time to spending it on a variety of excellent causes. These include: creating the "alt" (for alternative) hierarchy in the Usenet discussion fora; open-source software; drugs law reform; philanthropy; and the Electronic Frontier Foundation (which last week won a notable concession from the Library of Congress to legalise the "jailbreaking" of one's iPhone – ie liberating it from Apple's technical shackles).

The Gilmore aphorism about censorship first saw the light of day in 1993 – in a Time article about the internet – and since then has taken on a life of its own as a consoling mantra about the libertarian potential of the network. "In its original form," Gilmore explains, "it meant that the Usenet software (which moves messages around in discussion newsgroups) was resistant to censorship because, if a node drops certain messages because it doesn't like their subject, the messages find their way past that node anyway by some other route." But, he continues, "The meaning of the phrase has grown through the years. Internet users have proven it time after time, by personally and publicly replicating information that is threatened with destruction or censorship."

The aphorism came up a lot last week following publication by the Guardian, the New York Times and Der Spiegel of extensive reports based on the stash of classified US military reports published on the WikiLeaks website. And of course in one sense this latest publishing coup does appear to confirm Gilmore's original insight. But at the same time it grossly underestimates the amount of determination and technical ingenuity needed to make sure that the aphorism continues to hold good.

The sad truth is that, in practice, it is now trivially easy to censor the web. In most jurisdictions all you need to do is pay a lawyer to send a threatening letter to the ISP that hosts an offending site. The letter can allege defamation, or copyright infringement or privacy violations or a host of other grounds. The details usually don't matter because, nine times out of 10, the ISP will immediately shut down the site, often without bothering to check whether your complaints have any validity. The reason: a legal precedent set by the so-called "demon internet" case, which established that an ISP may be held liable for damages if it fails to act on a complaint. Most companies won't want to take the risk, so they pull the plug. QED.

So if the WikiLeaks operation depended on simply putting stuff on a website, then the governments and corporations who feel threatened by its exposures would have easily wiped it out years ago. Its durability is a product not just of the commitment of the activists behind it, but also of a sophisticated technical infrastructure which uses cryptography to ensure that every node in its virtual pipeline except the final, public, site is virtually impossible to identify.

At the heart of this is Tor, an open-source implementation of a networking technology which uses cryptography to pass data from router (internet node) to router in such a way that the identity of each is hidden. (The technology is derived from an earlier, multi-layered approach known as "the onion router" – hence the acronym.) As luck would have it, Tor is also a technology routinely used by governments to pass secret information around, so there's a nicely ironic side to WikiLeaks' deployment of it.

Tor provides a way of publishing information so that it's extremely difficult to trace content to a particular internet address. This is good news for WikiLeaks geeks, but less so for the average whistleblower because it requires a level of technical expertise most people don't possess. Which is why most whistleblowers will have to rely on the old-fashioned approach of putting stuff on lots of websites and social networks in the hope that it will be widely replicated. This may ensure that John Gilmore's aphorism continues to hold. But it will also mean that the whistleblowers' identities will be exposed. So if you have anything to reveal, try sending it to WikiLeaks first.