When the bots attack! [closed]

Question

What are some popular spam prevention methods besides CAPTCHA?

Answer 1

Use something like the google image labeler with appropriately chosen images such that a computer wouldn't be able to recognise the dominant features of it that a human could.

The user would be shown an image and would have to type words associated with it. They would keep being shown images until they have typed enough words that agreed with what previous users had typed for the same image. Some images would be new ones that they weren't being tested against, but were included to record what words are associated with them. Depending on your audience you could also possibly choose images that only they would recognise.

Answer 2

Honeypots are one effective method. Phil Haack gives one good honeypot method, that could be used in principle for any forum/blog/etc.

You could also write a crawler that follows spam links and analyzes their page to see if it's a genuine link or not. The most obvious would be pages with an exact copy of your content, but you could pick out other indicators.

Moderation and blacklisting, especially with plugins like these ones for WordPress (or whatever you're using, similar software is available for most platforms), will work in a low-volume environment. If your environment is a low volume one, don't underestimate the advantage this gives you. Personally deciding what is reasonable content and what isn't gives you ultimate flexibility in spam control, if you have the time.

Don't forget, as others have pointed out, that CAPTCHAs are not limited to text recognition from an image. Visual association, math problems, and other non-subjective questions relayed through an image also qualify.

Answer 3

The following is unfeasible with today's technology, but I don't think it's too far off. It's also probably overkill for dealing with forum spam, but could be useful for account sign-ups, or any situation where you wanted to be really sure you were dealing with humans and they would be prepared for it to take a few minutes to complete the process.

Have 2 users who are trying to prove themselves human connect to each other via their webcams and ask them if the person they are seeing is human and live (i.e. not a recording), by getting them to, for example, mirror each other's movements, or write something on a piece of paper. Get everyone to do this a few times with different users, and throw a few recordings into the mix which they also have to identify correctly as such.

Answer 4

Honeypot techniques put an invisible decoy form at the top of the page. Users don't see it and submit the correct form, bots submit the wrong form which does nothing or bans their IP.

Answer 5

Give the user the possibility to calculate:

What is the sum of 3 and 8?

By the way: Just surfed by an interesting approach of Microsoft Research: Asirra.

http://research.microsoft.com/asirra/

It shows you several pictures and you have to identify the pictures with a given motif.

Answer 6

Sblam is an interesting project.