An intruder broke into the New York Times intranet recently. Not that it was difficult, it seems. He managed to gather all kinds of confidential information about Times op-ed contributors etc. but did no real damage — and alerted the newspaper to the vulnerability he’d been able to exploit. But what if he’d got to the website and subtly altered Times copy? This highlights the risk of what Bruce Schneier calls ‘semantic attacks’. It means that we may need to become more vigilant about what we read online.