Mail Submission Protocol

Franck Martin franck at
Wed Apr 21 21:54:37 CDT 2010

If you have left port 25 open, this is a good place to start.

I suspect any decent IDS will tell you which machine has weird traffic. I suppose you can put rules based on the IDS result to redirect them to a special web page to tell them, they have to do something.

The main issue, it not to know which machines are hijacked, but to support these machines.

----- Original Message -----
From: "Suresh Ramasubramanian" <ops.lists at>
To: "Alex Kamiru" <nderitualex at>
Cc: nanog at
Sent: Thursday, 22 April, 2010 1:35:56 PM
Subject: Re: Mail Submission Protocol

Log and monitor all that you can. And watch for a large number of IPs
logging into an account over a day (over a set limit - even across
country - that takes into account "home - blackberry - airport lounge
- airport lounge in another country - hotel - RIPE meeting venue"
type scenarios).

And especially watch for and/or firewall off logins from areas from
where you see particularly high levels of smtp auth abuse / logins to
compromised accounts


2010/4/21 Alex Kamiru <nderitualex at>:
>>>Inside customers, we have not changed to force port 587 and
>>>authentication for email clients, but the topic has come up in
>>>discussions. This won't of course, stop spammers if they are
>>>hijacking the users local email client settings.
> How best would you stop spammers hijacking local users email clients
> -Mike

More information about the NANOG mailing list