Michael McCarthy: Just one click... and the worm can eat your machine

It may have been the world's biggest cyber-conspiracy, but it didn't need to involve genius (of the evil sort). Just plausibility.

Here's an email from your bank, for example, asking you to verify your password. Seems routine enough. Seems authentic. And you're busy. So yeah, do that. Click.

But click and you may be lost. For the basis of penetration of the vast computer networks of campaign groups, businesses, armed forces, even national governments, is often simply "social engineering" – sending out emails purporting to be from someone else. And once the recipient clicks on the attachment, hostile software – malware, in the jargon – inserts itself into their system.

We've grown more sophisticated and more aware of internet fraud. There can be few people who are now excited to receive an email offering 10 per cent of the sum of TWENTY FIVE MILLION DOLLARS! for use of a personal bank account to transfer the cash out of a dodgy place. These days, we look at that and laugh.

But cyber-pirates are growing more sophisticated themselves, and the killer email which worms its way into a system to do untold damage these days may look very authentic. In a report published yesterday, on electronic infiltration of the Free Tibet movement – part of the major Chinese-based cyber-conspiracy – computer experts Ross Anderson from the University of Cambridge and Shishir Nagaraja from the University of Illinois show that sometimes hostile hackers can get hold of a genuine email and add a hostile programme. The result is a hostile infiltration. In their report, "The Snooping Dragon: social-malware surveillance of the Tibetan movement", they write: "This combination of well-written malware with well-designed email lures which we call social malware, is devastatingly effective. Few organisations outside the defence and intelligence sector could withstand such an attack." Governments can mount such an assault, they say, but so could "a capable motivated individual".

Anderson and Magaraja point out that once hostile hackers have made an initial breach, once a single careless employee clicks on the wrong attachment – they can get inside it and use the knowledge they gain to disguise future attacks. "Prevention will be hard."

The lesson is twofold. One: always treat emails from people or organisations you don't know as suspicious, particularly if they have attachments. And two: fooling you is easier than you think.