Skip to main content

CAPTCHAs

"CAPTCHA" stands for ""Completely Automated Public Turing test to tell Computers and Humans Apart". You've likely seen them; web sites use CAPTCHAs to verify that a visitor is human (rather than a computer).

Here is an example of a CAPTCHA:

CAPTCHAs are an attempt to prevent computer-generated spam and other hijinx. Unfortunately, they cause several problems of their own:

  1. They decrease usability by adding to the amount of time and effort it takes for users to accomplish their goals.
  2. Some are difficult for humans to read.
  3. Some computer programs are better able to read them than humans.
Avoid CAPTCHAs if you can find an alternate way of preventing spam.

Comments

Chip said…
There was a guy at the first BarCamp Austin that was talking about one technique spammers use to get around captchas. Imagine a spam farm that has lots of open http sessions with sites that have captcha defenses. The farm is also a web site that advertise links to free porn. When people come to get the porn, the spam webserver shows them one of the captcha images and says "just tell me what it says to get your free porn." the spam-server takes the input and sends it on to the target site. ba-dow! more spam misery cuz you can't stop searching for free pictures of screech and mr sanchez.

Popular posts from this blog

Why Spreadsheets Suck for Prioritizing

The Goal As a company executive, you want confidence that your product team (which includes all the people, from all departments, responsible for product success) has a sound basis for deciding which items are on the product roadmap. You also want confidence the team is prioritizing the items in a smart way. What Should We Prioritize? The items the team prioritizes could be features, user stories, epics, market problems, themes, or experiments. Melissa Perri  makes an excellent case for a " problem roadmap ", and, in general, I recommend focusing on the latter types of items. However, the topic of what types of items you should prioritize - and in what situations - is interesting and important but beyond the scope of this blog entry. A Sad but Familiar Story If there is significant controversy about priorities, then almost inevitably, a product manager or other member of the team decides to put together The Spreadsheet. I've done it. Some of the mos

Stop Validating and Start Falsifying

The product management and startup worlds are buzzing about the importance of "validation". In this entry, I'll explain how this idea originated and why it's leading organizations astray. Why Validate? In lean startup circles, you constantly hear about "validated learning" and "validating" product ideas: The assumption is that you have a great product idea and seek validation from customers before expending vast resources to build and bring it to market. Indeed, it makes sense to transcend conventional approaches to making product decisions . Intuition, sales anecdotes, feature requests from customers, backward industry thinking, and spreadsheets don't form the basis for sound product decisions. Incorporating lean startup concepts , and a more scientific approach to learning markets, is undoubtedly a sounder approach. Moreover, in larger organizations, sometimes further in the product life-cycle, everyone seems to have an opinio

What Product Managers Can Learn from the Apple iPod

The Story When Apple unveiled its iPod digital music player back in October 2001, I dismissed it as a  parity product . I already owned the Cowon iAUDIO CW100 MP3 player, loaded with my favorite tunes. There was Apple, generating great hype over the iPod as if it were a breakthrough product. The idea of a portable digital music player was nothing new. The first mass-produced MP3 players came out in 1998. In late 2001, the concept may have been new to a lot of Apple customers, but it wasn't new to me. I proudly showed my MP3 player to friends when they gushed about the iPod. Thus Apple's iPod was not an innovative product in and of itself. Years later, however, I realized the significance of ecosystem of which the iPod was a part. Apple had released iTunes (with technology purchased from  SoundJam MP ) and created the iTunes Store for finding and downloading music. Unlike Napster , it was a safe and legal way of distributing and acquiring music. The prior way of playing