![]() Furthermore, none of these are particularly difficult CAPTCHAs. And that level of CAPTCHA security is absolute overkill unless you happen to run one of the top 100 most popular sites on the internet. #Solve captcha with flash image plus#Still, it's unlikely that any OCR engine could beat high perturbation – where the characters are physically overlapping each other – plus a little background noise. #Solve captcha with flash image free#I'm sure there are more advanced OCR engines out there that might be able to do somewhat better than the free SimpleOCR engine. Adding a tiny bit of noise or perturbation to the CAPTCHA text was all it took to break the OCR. I didn't expect it to do well, but I was frankly surprised how poorly the SimpleOCR engine actually performed. Note that these CAPTCHAs all use the same font, Courier New. Here are the results of submitting a few standard 180x50 CAPTCHAs from my reworked rendering algorithm. ![]() SimpleOCR has an online form that allows you to upload and OCR small greyscale TIF images. I've been experimenting with improving the rendering algorithms in my CAPTCHA server control, and it's interesting how fragile typical computer OCR really is. I went from cleaning up comment spam every day to cleaning one per month. But it's still strong evidence that moving the difficulty bar up even one tiny notch can be quite effective in reducing spam. Granted, Yahoo is more popular than my blog by many orders of magnitude. I can count on two hands the number of manually entered comment spams I've gotten since I implemented it. This has to be the most ineffective CAPTCHA of all time, and yet it stops 99.9% of comment spam. The comment form of my blog is protected by what I refer to as "naive CAPTCHA", where the CAPTCHA term is the same every single time. And if CAPTCHA is so thoroughly defeated, why is it still in use on virtually every major website on the internet? Google, Yahoo, Hotmail, you name it, if the site is even remotely popular, their new account forms are protected by CAPTCHAs. Some people actually believe that spammers can now "fairly easily" write scripts which use advanced optical character recognition to automatically defeat any online CAPTCHA form.Īlthough there have been a number of CAPTCHA-defeating proof of concepts published, there is no practical evidence that these exploits are actually working in the real world. There's a popular misconception in technical circles that CAPTCHA has been "broken": CAPTCHA, which stands for (C)ompletely (A)utomated (P)ublic (T)uring test to tell (C)omputers and (H)umans (A)part, works well for small sites but larger 'community' sites where there are multiple SPAM targets CAPTCHA only provides a false sense of security - it can be broken fairly easily and serious spammers are getting more sophisticated all the time. ![]() They're a necessary evil, just like the locks on the doors to your home and your car.ĬAPTCHAs are designed to discriminate between computer scripts from spammers and real human beings. If you've used the internet at all in the last few years, I'm sure you've seen your share of CAPTCHAs: ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |