Hi Temp,

that’s a bad idea. I have a lot of anti-spam measures implemented in my forum (regexes for suspicious e-mails and names [1], a local list of nasty e-mails [2], a daily updated local copy of StopForum’s banned IPs [3], querying the e-mail address at SFS [4] and BotScout [5], filling out the registration form in <2 seconds [6]) and keep a log-file of rejected registration attempts. Since mid-October last year I blocked ~4,200 attempts.

You don’t want to go there.

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Bots for sure. On the average it takes them 3.3 milliseconds to register (0.35–16.8 ms). Breakdown of my log-file:
[1]   6.4%
[2] 13.6%
[3] 61.6%
[4] 14.3%
[5]   0.6%
[6]   3.6%

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I’m considering to switch off everything excepting the timings. If a registration takes milliseconds, that’s a bot. Full stop.