[pmwiki-users] Captcha: IP blocking

Marcus prima at wordit.com
Mon Sep 1 18:21:29 CDT 2008

Is there a way to block an IP address after the user has failed to
respond correctly after a certain number of attempts?

I have been working on challenges for the linguistic (text-based)
Captchas. Since the responses are words from the dictionary it might
be a good idea to limit the number of attempts to prevent spambots
from hammering away at the site with a dictionary attack. One could
ban the IP for a certain time.

Anyway, I have now what I think should be good linguistic challenges.


- When does the sun rise? In the ...

Requires simple world knowledge, which is the same everywhere.

- John and Mary were married last week. Mary is now John's ... (Or
John is now Mary's ...)

Requires understanding of the relationship between people and events
which took place, but a child can answer. Also no cultural boundaries,
AFAIK. Those who do not understand will also lack internet access.

- Claire ran out of her bedroom and down the stairs into the kitchen.
Claire's bedroom is located u...

Scene-based: A scene is described and the user must answer based on
comprehension of the scene. I think this is the most promising and
most difficult challenge for a spambot to crack. It's not possible
without advanced linguistic AI.

Does anybody, particularly non-native speakers of English, have any
difficulty answering this question?

Anyway, what I'd like to do is count the failed response attempts and
block IPs accordingly.


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