Illustration: Liu Rui/GT

Pity the poor aspiring adulterers who signed up to US matchmaking site Ashley Madison. The booming service, whose slogan is "Life is short. Have an affair," promises to match horny husbands with willful wives, and pledges the utmost discretion. It markets itself to anyone in a relationship, not just the legally married, but its user base appears to be largely straight, male and wed.

But while in the past cheaters just had to watch out for grubby detectives and town gossips, the Internet had broadened the scope of potential exposure. The site has been hacked and the culprits, who call themselves "The Impact Team," have threatened to post the payment details of 37 million users, along with the detailed questionnaires they filled in about their sexual fantasies, online.

It's easy to laugh at the misfortune of the wannabe cheaters who turned over their data to Ashley Madison. For some, it seems like they brought it on themselves with their quest for a bit on the side, and this is a form of karmic justice. Now their desires threaten to be laid bare before friends and family.

Ashley Madison said they could provide the utmost anonymity, including a service - with an $18 charge - that would completely wipe your account. It's this offer that the hackers claim stirred their ire, since, according to their manifesto, users' "purchase details are not removed as promised, and include real names and addresses." There is, apparently, an option for anonymous payment services, but few users took it, instead trusting a site that boasted of its security awards on its homepage.

But the truth is that all of us take a massive risk anytime we thoughtlessly hand over our personal information. And everywhere is potentially vulnerable, no matter how many promises a site might make. Ashley Madison have blamed a "disgruntled former employee," a common claim after such security failures. There's a lesson in this; no matter how good security precautions are, inside incompetence or deceit can open anything up. Think of the briefcases full of data accidentally left on public transport by British civil servants. Even the best design systems fail sometimes, and most of them aren't that well designed.

Then there's the technological mistakes that expose embarrassing secrets. Take the Facebook app originally called "Bang with friends," which let you choose which of your Facebook buddies you wanted to sleep with, promising to send you both a notice if they used the app and also noted they wanted to sleep with you. It promised anonymity - and then a new Facebook service, Graph Search, set privacy settings to default and allowed anybody who wanted to see who their friends using the app wanted to sleep with.

Not dumb enough to put the details of who you want to bed online? Your secrets are still out there. Unless you're taking extreme measures, the vast web of data we generate for firms everyday makes it easy to pinpoint you and identify your habits, whether that's a fondness for ordering sweets online or a liking for romance novels about dinosaurs.

We pay for the "free" services we enjoy, like Facebook, by handing them data about ourselves. They share it with others, including advertisers, and controls over just who can see it are often far scantier than the sites claim. Julie Angwin's book Dragnet Nation, where she attempts to track exactly how much data she'd unwittingly left online, shows just how much information all of us produce just through our everyday browsing. 

So we shouldn't judge the cheaters of Ashley Madison too harshly - at least for their naiviety about privacy, if not their sexual ethics. They simply falsely believed the same promises all sites make; privacy, security, safety. There's one clear lesson here; if you want to screw around it's better to do it the old-fashioned way. Surely there's a boom business here for sleazy hotel bars?

The author is an editor of the Global Times. jamespalmer@globaltimes.com.cn