On 30 Nov 2005 at 20:23, Marten Lehmann wrote about
    "[exim] limiting messages send by ce":

| we are hosting websites of several thousand customers and a few of them 
| are obviously using insecure formmail scripts. While it's impossible to 
| get rid of all formmail-scripts, I'm thinking about a solution within 
| the mta (exim) to limit the messages that may be send within a certain 
| period.

What I do is check the the number of recipients per message, and 
reject if it is over a very small number (3).  The idea is that web-
form email is only intended to be sent to one or two recipients (e.g. 
"submit this support question, and send me a copy").

verify = header_syntax is also very good at catching emails generated 
by an abused formmail script.  That's because such messages generally 
have duplicate headers - the legitimate headers generated by the 
script and the headers injected by the abuser.

|...

- Fred





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