Mailing List Archive: 49091 messages
  • Home
  • Script library
  • AltME Archive
  • Mailing list
  • Articles Index
  • Site search

[REBOL] Re: Preventing Automated Website Registrations

From: joel:neely:fedex at: 8-May-2002 14:32

Hi, Ted, Here's a quick-and-dirty solution that avoids the need for any on-the-fly image generation (which means it will run faster, in all likelihood). Thaddeus Serpa wrote:
> In a nutshell, the program generates an image containing some > effects and a word within the image. The user has to enter the > word in a text box. Since computers aren't able to decipher the > word, it's a safe bet that the user is actually a human > registering at the site and not an automated program. >
> Unfortunately, I don't have the knowledge to do this myself. Can > anyone offer some assistance? >
Some background: A few years back I wanted to add a fancy-looking hit counter to a page, but without the overhead of the image processing. I created a separate image file for each digit value and a blank (let's call them 0.gif, 1.gif, .... 9.gif, and blank.gif for the sake of discussion). The script would calculate the number to be presented (let's say 2413 for example) and would generate html something like the following: <table cellpadding="0" cellspacing="0" border="0"> <tr> <td><img src="blank.gif"></td> <td><img src="blank.gif"></td> <td><img src="2.gif"></td> <td><img src="4.gif"></td> <td><img src="1.gif"></td> <td><img src="3.gif"></td> </tr> </table> The results appeared essentially the same as a single custom-built image, but required no server-side graphics code. Now, in your case, you could have one (or more) image(s) for each letter of the alphabet, and simply send a sequence of IMG tags, perhaps wrapped in a table, to spell out a human-readable message which wouldn't be visible to a 'bot. Of course, you'd want to call them something besides a.gif, b.gif, c.gif, etc. to avoid giving hints to the bad guys. The point of having multiple images for each letter would be to allow the same human-readable code to be "spelled" out in many different ways, again making it harder for some nasty character to figure out how to write custom code to interpret the html from your site. Hope this helps! -jn-