I hate CAPTCHAs
|
| Author | Content |
|---|---|
| Sander_Marechal Apr 14, 2008 1:37 PM EDT |
I really hate CAPTCHAs. Besides, most of them are easy (not trivial, but not hard either) to crack automatically. Besides, most websites out there that use CAPTCHAs don't need them. I don't use them on my blog either. I've written a custom spam filter for my comments that's pretty hard to beat. I think I have about 500 comments overall on my blog, of which 300 were spam. My filter had about two false negatives (let spam through) and one false positive (stopped a valid comment). I don't have to annoy my visitors with CAPTCHAs. My filter uses a variety of techniques, integrating with Akismet, Linksleeve, Spamhaus and a bunch of custom filters. The problem with the CAPCTHA libraries in the article is that they are libraries. It's incredibly hard to write a generic CAPTCHA solver [*] but not relatively easy to write one targeted at a specific library. Widely used libraries tend to have CAPCTHA solvers written for them, so if you use one of those generic libraries then all a spammer has to do is figuring out which library you used. Do yourself a favour: If you use one of these libraries, change the code so it generates different images from the standard set of options provided by the library. It's not fool-proof but at least you're reasonably safe from the script kiddies that use the standard toolkits. [*] The most inventive way I've ever seen was a ring of porn websites run by spammers. Write a web crawler looking at sites you want to spam. Save the CAPCTHA image to your central server. Put the CAPTCHA on your porn site. Have the porn site visitor solve the CAPCTHA for a few extra hawt nudie pics and use that result to spam the original website. You can't beat this system. |
Posting in this forum is limited to members of the group: [ForumMods, SITEADMINS, MEMBERS.]
Becoming a member of LXer is easy and free. Join Us!