Captchas

Van Hellseek

Van Hellseek

Van Hellseek

Soldato
Joined
2 Jun 2004
Posts
18,423
Keycaptcha or solvemedia (or other)?


Personally I think solvemedia is infinately better since it's never difficult to read. I can typically get past solvemedia in 2-4 seconds, but keycaptcha often takes 10+ due to needing to refresh it until it displays something readable.

What do you use on your sites, and are you happy with it?
 
I used to use recaptcha I found it was easy enough to read and liked the idea behind it but recently it's getting more and more difficult to read so I have removed it. Now I'm using Personalised questions something like an maths question or "Who designed this website the name is in the footer" etc. Just as the captchas annoy me so much when your spam clicking to find a readable one.

Mark
 
I find that the best thing I did on the forum I manage is to add one of the custom text questions as Mark H has also noted.

It should be a question that's very easy for a human to answer, but where the answer can't be retrieved from a Google etc search.

One I went through earlier was "What is the fourth word in this sentence?" :)
 
If your site doesn't get much traffic then a custom question is the best solution. Obviously it would be trivial for someone to code a bot to answer it but you've got to consider that someone probably isn't going to bother for such little return.
 
You don't make money from these 'random question' things though.

The solvemedia subliminal advertising is interesting. Like "enter the product slogan to continue".

The best way to remember something is to write it after all! :D

(captchas are not just about preventing bot spam)
 
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Van Hellseek said:
Looks easy, yes. But is it actually?
Click to expand...

Yes. Easy to segment and absolutely no noise. You can train neural networks to outperform humans when it comes to identifying characters in noisy environments, there's plenty of research on this. The key defence is preventing segmentation (isolating each character) which that CAPTCHA doesn't even attempt in most cases.

I've flicked through a few more and I really wouldn't be surprised if standard off-the-shelf OCR could read enough of them to obtain a very handsome pass rate.
 
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So why would a relatively large site like tinypic use it then? They originally used keycaptcha, but switched to solvemedia at least a year ago. If it was really that easy for bots to bypass they wouldn't use it.

Also, you think www.solvemedia.com hasn't already thought of this? :confused:
 
I would imagine they switched because keycaptcha is quite time consuming as well as the financial incentive for moving over to solvemedia.

All due respect I'm not going to summarise all of the research papers I read on the subject in my final year of uni. You can do your own research if you want to find out why it isn't a good CAPTCHA.

It's pretty simple really: if you as a human find it easy to read then it's relatively easy to create a program to solve them.
 
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The company I work for sell a product that is specifically designed to read the unreadable labels of packages. We take images of illegible writing, damaged letters, etc and produce legible 1-bit per pixel images that amaze everyone we show it to.

Software is getting better at reading characters than the human eye is.

Plus there is always the mechanical turk that will never be beaten.
 
sniffy said:
It's pretty simple really: if you as a human find it easy to read then it's relatively easy to create a program to solve them.
Click to expand...

All I'm going to say about it is; solvemedia know more than both you or I about this. And if it was really that simple they would do things differently.
 
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Van Hellseek said:
And if it was really that simple they would do things differently.
Click to expand...

I just got a 50% pass rate on 6 of their CAPTCHAs using an opensource OCR software called Tesseract. Try it yourself if you don't believe me, only takes a few minutes. I'm not sure what you're having difficulty understanding though as it's clearly not a good CAPTCHA. How do you think normal OCR works if it's going to fail on these CAPTCHAs. I mean really... Perhaps you're kidding yourself because of the financial incentive. Needless to say if anyone wants to automate sign-up of your site they can easily do it. It will simply be a way of getting some pocket change from your users. They also have moving CAPTCHAs. I hope I don't have to explain why that is pointless.

Edit

Perhaps I've been thinking about solvemedia's apporach wrong. Maybe sites like tinypic weigh up the money lost from having automated uploads against the money gained from having the CAPTCHAs solved and the latter outweighs the former.
 
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I'd be curious to know the number of accounts registrations that get through to the moderation queue with both the random question and NoSpam question - simply enabling one or the other on forums I've administered in the past have seen an instant reduction in successful registration processes from bots from hundreds per day to, well... a couple a month.

With these simple options, as well as the restriction that OcUK places on throw-away email addresses (well, they used to, not sure if they do now), I wonder what the addition of a further image-based Captcha would do...
 
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