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

Henry Ford's "Faster Horse" Quote

You may have heard the ( apocryphal ) Henry Ford quote: If I'd asked customers what they wanted, they would have said "a faster horse". Over at the On Product Management blog , Saeed gives his take on this infamous quote. He "hates" it, and gives some compelling reasons. Saeed is spot on in his explanations. Personally, I think the quote is great, but it's a matter of interpretation. The valid point of the quote is not that it's a bad idea to facilitate a conversation with your market to better understand it. The valid points are: You must ask the right questions to get valuable answers. You must interpret the answers thoughtfully - often outside their direct meaning - to glean reliable information. Asking questions is not always the best way to "listen" to your market. (E.g., sometimes pure observational studies are more reliable.) Nonetheless, I find the quote is helpful to combat "armchair product management" in the

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