Re: SMTP decoder

["Joel Esler (jesler)" <jesler () cisco com>]

You’ve got your two alternatives there.  Raise the limit, or suppress the alert.

Ask yourself what your action is going to be there.  “What am I going to do about a big SMTP server command”, if the 
answer is “nothing”, then suppress the alert.  If the answer is anything else, then use your best judgement as to what 
action you should take.

--
Joel Esler
Open Source Manager
Threat Intelligence Team Lead
Talos

On Feb 11, 2015, at 9:51 AM, Dan Roberts <danroberts2604 () gmail com<mailto:danroberts2604 () gmail com>> wrote:

Hello guys,

I'm running SNORT since a few months now, and I still get a lot of alerts like:

"(smtp) Attempted command buffer overflow: more than 512 chars ...."

In the snort.conf file, we find following parameter for the smtp decoder:

"max_command_line_len 512"

Although the maximum command line length is "strictly" limited to 512 by RFC 821 (HELO), the RFC 1869 (EHLO) authorize 
the extension of this limit:
... This specification extends the SMTP MAIL FROM and TO to allow additional parameters and parameter values. It is 
possible that the MAIL FROM and RCPT TO lines that result will exceed the 512 character limit on command line length 
imposed by RFC 821.
..."

How do you,  guys, manage this ?

Do you simply consider these alerts as FP ?
Have you raised the max_command_line_len limit ?

Cheers
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