What is a CAPTCHA anti-spam system?
My system administrator is telling me that I need to add a "capcha" [actually, it's "captcha"] system to my site so that I get less spam. What's a captcha system and why would I want it?
Ah, spam, the bane of our collective online existence. It's a pain and it's frustrating how much time and effort we have to collectively expend trying to minimize its impact on our online experiences. Blech.
Here's a fun fact that most people don't know: CAPTCHA is actually an acronym. It stands for "Completely Automated Public Turing test to tell Computers and Humans Apart." (Turing here refers to the brilliant computer scientist Alan Turing, who spent much time thinking about how to differentiate really smart computers from humans, to so-called "Turing test").
I know you've seen these. Here's a typical CAPTCHA from Google's site:
The basic idea is that it's some twisted or distorted or obfuscated text that you, as a human, will have no problem recognizing, but that a computer program would have a very tough time interpreting: if it can't figure out the words shown, it can't pretend to be a human and therefore can't spoof the system.
Here's another example, from Craigslist:
This one is more interesting in some sense because it's the same basic idea, but this recaptcha is actually also a distributed solution to interpreting difficult-to-read scanned text in old books being digitized. Nice win:win!
Lots of sites use these, actually. Here's one from Facebook:
Unfortunately, the simpler CAPTCHA systems have been cracked through various means, ranging from smart image scanning and analysis software to brute-force guessing (mapping captcha image file name with a solution) to simply showing the CAPTCHA in another context on an apparently innocent Web site and storing the values [innocent] people type in.
MySpace is late to the party, but its system is pretty typical:
Earthlink is a bit more colorful:
And, finally, here's what Yahoo uses:
They're all using the same basic concept and it works, though it can definitely be frustrating when they twist or distort the text too much and just cause a headache.
I would say that if you are having spam problems on your site, it's quite probably from automated tools pretending to be humans, and a CAPTCHA system might well be just what you need to make the problem disappear.
If only it were so easy to make the spammers disappear.
More Useful Computer and Internet Basics Articles:
✔ How do I blur my house on Google Maps Street View?
I was poking around on Google Maps looking at satellite views of my neighborhood and when I switched to street view, was upset...✔ Create a custom vanity URL for Kickstarter?
I was reading some updates on Twitter and saw someone had posted a URL that would let me see what projects they'd backed...✔ Export or Save Subscription List from Google Reader?
Just heard that Google Reader is going away this summer. That stinks! How am I supposed to read my RSS feeds? More importantly,...✔ Shrink or Reduce a Photo File Size on Mac?
I'm trying to upload some photos to a social media site and it's complaining that they're too big. They are, as they come...✔ Can I organize my Yahoo Mail with folders?
I've been on Yahoo Mail for years and while most of my friends are now on Gmail or their own Web-based email programs,...
Let's stay in touch!
Sign up for my weekly AskDaveTaylor Newsletter and you'll receive even more tech and gadget help right to your inbox, along with exclusive news and industry updates. It's good stuff. I promise!
I do have a comment, now that you mention it!
Check This Out Too...
Look for Answers
All Our Categories
Apple iPad Help
Articles and Reviews
Auctions and Online Shopping
Blogs and Blogging
Building Web Site Traffic
Business and Management
Computer and Internet Basics
d) None of the Above
Google Gmail Help
Google Plus Help
Industry News and Trade Shows
iPhone and Cell Phone Help
iPod, Sony PSP and MP3 Player Help
Kindle Fire Help
Mac OS X Help
Pay Per Click (PPC) Advertising
Search Engine Optimization (SEO)
Shell Script Programming
Tech Support Video Help
The Writing Business
Twitter, LinkedIn and Social Network Help
Unix and Linux Help
Video Game Tips and Help
Windows PC Help
Find Me on Google+
ADT on G+