Suspicious membership applications

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This is a drupal question asked by kgg on 08 February 2010

I have a Drupal site to represent our local electric vehicle interest club on the internet. Membership is set up to require approval, and there is a message on the registration page stating that the site is only for local interests. Despite this, there have been several registrations from unknown people with email addresses that look like they border on hackers/spammers.
Also, none of them have contacted me complaining about continuing to be blocked.
This has made me suspicious that there may be exploits that they know about. Of course, they could be on the look-out for sites where the permissions are not properly set

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