End of the road for Captchas?

Question

If you've made quick edits to answers recently here on SO, you've probably noticed that the captchas have gotten to the point where even a human needs to hit reload several times to find a readable one.

It occurs to me that if this level of smudging is required to get past OCR software today, then the day isn't long off where computers will be better at reading captchas than humans are. Basically, they will probably be useless in a matter of weeks from now. What are those of us who use them to filter automated spam going to do then?

Answer 1

I doubt it.

Answer 2

When computers can read obscured text better than humans, you move on to different captchas. I once saw a captcha in which you had to count the number of cats in the picture.

Eventually someone will produce strong AI that is at least as intelligent as a human, but at that point I think we'll need to be more concerned with a robot uprising than spam.

Answer 3

End of the road for visual captchas? maybe.

Logical ones can take their place. Gotta love the "answer me these questions three" approach that is needed. Asking people to answer riddles might work. Mixed in the pot with other things.

Answer 4

Short answer: yes, captchas are doomed, and I have no idea how to replace them.

Robots are tenacious little beasts, and are perfectly happy trying something over and over. This means that any little Turing test cannot be multiple choice, and must be available in large quantities.

Suppose you have a multiple-choice Turing test with ten possible answers. This means that, at worse, a bot has a 10% chance of solving it. This means the bot only has to hammer your servers ten times as much to get in. For your typical bot, this isn't a problem.

Suppose you have a limited number of captcha-replacements. These can be fairly easily programmed in, so that the bot knows that a JPEG with this checksum requires that answer.

Now, another requirement is that a captcha-replacement has to allow real humans to solve it. This means that it can't be too demanding. If you display a picture of, say, a Boeing 747 and ask what it is, you have to be prepared for answers like "airplane", "aircraft", "aeroplane", "airliner", "Boeing 747", "747", "passenger plane", "Airbus", and so forth, since different people will answer in different ways, and people aren't always perfect in their understanding.

It also means that any of these devices can be solved by other humans, either working for pennies in poor countries, or by solving echoed versions to get into porn sites (both techniques have been used).

Answer 5

Captchas were doomed from day 1, since it's always possible (given a good reason & resources) to hire cheap labor to solve it for you. I won't enlist the solution here, but the trick has been invented and implemented years ago.

The crux of all doors and barriers isn't about blocking, but about the cost to either side to overcome the barrier.

if a safe is too expensive to crack, but cheap enough for you, the thief won't take it.

Answer 6

Yea, captchas are to the point now where they are much more an annoyance than any kind of real deterrent. In an ideal world, the future that would replace it would be some kind of biometric validation against a secure central source. Sort of like trusted certificates. The technology is available and has been for a while to do this effectively, but wide-spread acceptance is a whole different issue. With concerns over privacy and identity security concern it is likely a long ways off still. But a device attached to your computer or even on your smartphone which does a retina scan or facial recognition and validates it against a secure authority to verify your identity would seem to me to be the ideal. Who knows... some day.

Of course, I think of how cool that would be, then I'm reminded of things like the "Minority Report" that take that kind of thing to potentially scary levels.

Answer 7

A bit off topic - but we had a phone call from a customer recently, who said that they couldn't get the letters at an angle, as they were in the captcha image. They had tried tilting the keyboard to no avail.

Personally, I find them to be awkward at times and just a temporary fix to the long-term problem of spam.

Answer 8

So maybe we'll live to see the day when genuine authentication is both

(a) required by websites (b) not considered a problem by users

Answer 9

The logical captchas seem to work imo. A phpBB3 MOD is out that I use on another forum and it adds a logical question that is left up to the board administrator to fill in the question AND answers (of course, lol).

I've got it setup to ask the user "2 + 2 = ?". Bots really don't know how to answer that and it really works in my experience. :P