[exim] rejecting dictionary attacks

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Autor: oliver howe
Data:  
Para: exim-users
Assunto: [exim] rejecting dictionary attacks


I have the following check for valid users in my configure file in the Routers section

check_valid_user:
driver = redirect
domains = mydomain.co.uk
require_files = !${perl {get_user_dir}{$local_part}{$domain}}
condition = ${if exists {perl {get_user_dir}{$local_part}{$domain}} {yes} fail}
data = :blackhole:

It uses perl to check they are valid on the system as the mail server punts the messages on to a different server that contains the actual mail directories. It works really well (has discarded over 200,000 messages so far today alone). Can I add anything to this router so that if it sees many such messages from the same host then it will ignore that host in future?

If I try and accept all such messages and bounce back a "unknown local-part in domain" error message then the rest of my network will grind to a halt.

Thanks,

Oliver


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Oliver Howe
Senior Systems Administrator

Tel: +44 (0) 20 7664 7811
Fax: +44 (0) 20 7664 7878

Spider Networks - the power behind interactive web communications - www.spider-networks.net


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