LL      IIIII NN   NN KK  KK EEEEEEE RRRRRR  RRRRRR   OOOOO  RRRRRR 
LL       III  NNN  NN KK KK  EE      RR   RR RR   RR OO   OO RR   RR
LL       III  NN N NN KKKK   EEEEE   RRRRRR  RRRRRR  OO   OO RRRRRR 
LL       III  NN  NNN KK KK  EE      RR  RR  RR  RR  OO   OO RR  RR 
LLLLLLL IIIII NN   NN KK  KK EEEEEEE RR   RR RR   RR  OOOOO  RR   RR
                                                           ramblings
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Posted on: Friday, June 4th, 2010 at 20:47.
Filed under: Coding, ServerAdmin, Software.
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When you’re running any type of shared hosting server, with hundreds of clients that have the ability to run php scripts, send emails, etc,… How do you make sure you’re not setting yourself up to be one big spam haven? (the true answer is: you don’t, since shared hosting is one big mess.- You’re screwed.) – A compromised script of a client could be sending out spam mail without using your MTA, so it would not show up in your logs or mailqueue.

For this reason I wrote a little perl script which sniffs all outgoing SMTP traffic and dumps it to a file. You could then set up a cron job which scans the file for known keywords used by spammers (viagra/v1agra/Vi4Gr4/etc…….) and alerts you when something is found; or you could make it extract the emails and run them through spamassassin.

This way, even if the outgoing traffic is sent by some script using sockets to connect to port25 of some external mail server, bypassing your mta, you will still know about it.

Just change the settings on top of the script to reflect the ip address(es) you’re using and the network interface open to the internet.

Download/View it here

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3 Responses to “Forensic smtp sniffing”

  1. mouser says:

    great work as always.

  2. BUGHUNTER says:

    Interesting to read about, but unfortunately the link to mailsniff.txt is dead…

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