Thread: Captcha recommendations and alternatives

What are the best captcha's or alternatives out there to help fight spam?

Originally Posted by Tom

What are the best captcha's or alternatives out there to help fight spam?

What system are you using ? language ... ? ... or is it for a custom build ?

Php and Javascript mostly but really any recommendations no matter what technology they use.

Came across a nice page with some tips here AS Workshop » The CAPTCHA Alternatives

this tip sounds good... quoted from above page

I am surprised no-one has mentioned a variation on the session idea where you record the time the form was loaded. Then on the post you calculate the time difference and if its less than say 5 seconds you ignore it as spam. Of course spam bots could easily adjust for this by building in a delay, but imagine if we all did this forcing all spam bots to work more slowly we could reduce the total amount of spam for everyone. Since implementing such a system about a week ago I have not had a single item of spam get through.

I just checked a lot of spam I've been receiving and unfortunately it seems to be 30secs or so apart, so either bots are now going slower to mimic humans or the spam was entered manually.

One of the things I do on here is check against DNS blacklists.

If someone's IP is listed in SpamHaus they're automatically banned when they try to signup

It means that the amount of junk posted is significantly lower!

I just wrote a custom challenge based one and it easily the best, simply and box to your reg page saying "What is 2 plus Three?" the in the reg page check for 5 or Five or five

They are good to a certain extent ... you need a fairly decent sized question base ... if you make it too difficult it will disuade users ...

some of the bots are already able to handle some of the challenges ...

the main commercial bot that i'd say is responsible for 85% of web spam can do those answer things. BotMaster.Net: captcha breaking, automatic recognition of pictocodes (human verification)

I don't really like the idea of asking questions or picking images, I worry that less web savvy folk might read it and think "What the heck is this? Why is this website asking me a silly question? What is 2+2? Or what year is it? Or pick the elephant." Even if you explain why I still don't think it looks the best, especially for certain types of sites.

Standard captchas have been around longer and I imagine more people would be used to them. Imo I think they look better than asking a silly question too.

I wonder how an animated gif or flash captcha might work, I haven't seen any of these in action. Surely they would be very hard for a bot to recognize and nearly everyone has flash these days.

There are a few animated captchas. Georgie Casey » Blog Archive » Most annoying captchas ever

They'd be easy enough for a bot to do if they could do static captchas. Captcha solvers are highly advanced, nothing really stopping them if the volume is there. So I'd say just use a unique captcha and the spammers wouldnt be bothered writing something to solve it.

Originally Posted by georgiecasey

There are a few animated captchas. Georgie Casey » Blog Archive » Most annoying captchas ever

Oh god ... I don't even think I'd get them right

Originally Posted by georgiecasey

They'd be easy enough for a bot to do if they could do static captchas. Captcha solvers are highly advanced, nothing really stopping them if the volume is there. So I'd say just use a unique captcha and the spammers wouldnt be bothered writing something to solve it.

I think the problem is bots can identify the captcha on your page ... its not whether you do a custom captcha or not ...

possibley saying please pick the first letter and last number from this image might work ... again you're making the user have to think about it all and as Tom said .. these days .. people are used to Catchas ...