Bugs are common in software, almost every program has one that exasperates its users. But truly unusual bugs that prompt technology to behave as if it was possessed are a rare breed. We round up nine of the most fascinating rare bugs.

Almost every software application in computing history has had a bug, which has irritated its users no end. However, occasionally you stumble across a truly interesting bug.

I'm talking about the kind that cause technology products and services to stop working for extended periods, or that prompt them to behave as if they were possessed or harboured grudges against the humans who use them. And even though the bugs themselves usually stem from mundane errors such as typos or faulty math, their symptoms are anything but boring.

For this story, I rounded up nine truly peculiar bugs that bedeviled customers of some of the largest providers of software and services on the planet. (I didn't cover ones with catastrophic side effects such as explosions, or the death of human beings).

Of course, when it comes to bugs, Windows occupies a whole category of its own. And sometimes the problem isn't a mistake so much as a really bad idea from the beginning.

I began my research intending to cover the whole PC era, but I quickly discovered that most of the strangest bugs have appeared in recent years. As a matter of fact, the three wackiest ones in my list - involving Google's Android OS, Microsoft's Zune and Google itself - all cropped up in just the past few months. I'm not sure if software is getting buggier, but I am pretty certain that bugs are getting weirder.

Our first bug, however, dates from a simpler time. One in which it didn't occur to software companies to do things like encrypt intensely sensitive information...

1995: Many unhappy returns

Intuit's MacInTax (a program later replaced by TurboTax) was designed to let Mac users file their taxes. But the version for the 1994 tax year had another feature, discovered by one taxpayer: it allowed any customer with a little telecommunications knowledge to dial in to a computer where 60,000 tax returns sat unprotected. Once in, a user could view any return, make changes, or simply erase the return entirely.

The bug: MacInTax was bundled with a debug utility intended to help customers diagnose modem problems. The utility dialed in to a server operated by an Intuit subcontractor. The utility used an account name and password that weren't encrypted or otherwise obscured, and that granted anyone who stumbled across them complete access to MacInTax users' data.

Intuit called the glitch "an oversight"- no kidding! - and apologised. The company offered to pay any penalties suffered by anyone whose return encountered problems as a consequence.

NEXT PAGE: Auction Interruptus

  1. These glitches are a rare breed
  2. Auction interruptus
  3. Skype down and out
  4. The day the Zunes stood still