[Snort-sigs] http post on port 25

Joe Patterson jpatterson at ...2901...
Tue Feb 8 11:58:32 EST 2005

I would bet I know what this is.  A spammer has found an open http proxy
server.  He is "requesting" the "document" located at
http://your.mail.server:25/ from that http proxy server, and part of the
POST operation just happens to be very similar to an SMTP conversation.

Probably handy to know about, if for no other reason than to build up a list
of open proxy servers out there.


> -----Original Message-----
> From: snort-sigs-admin at lists.sourceforge.net
> [mailto:snort-sigs-admin at lists.sourceforge.net]On Behalf Of hans
> Sent: Tuesday, February 08, 2005 11:42 AM
> To: snort-sigs at lists.sourceforge.net
> Subject: [Snort-sigs] http post on port 25
> hi all
> this days i noticed some strange dialogs on smtp port 25
> hosts around the world are trying to setup a dialog
> immediatly after the SYN - SYN ACK - ACK frames
> with the following content:
>  POST / HTTP/1.1
>  Host: my.hostname.com:25
>  Content-Type: text/plain
>  ... and so on
> o.k. - i am not crazy, i really speak about e-mail, and
> this is not the content of the message body, it's the tcp-flow
> later in the dialog there is a rset, but game over
> with sendmail and greeting feature.
> there are some additional infos, like a tcpdump and a rule for
> snort, to find at  http://ma.yer.at/2005/smtp_post.html
> i would be interested, if you could also notice such traffic.
> i can't belive, are there any mail-gateways, which respond to
> http-post-commands on port 25 ?
> here the rule, which does the job for me perfectly:
> alert tcp $EXTERNAL_NET any -> $SMTP_SERVERS 25 (msg:"SMTP POST";
> flow:to_server,established; content:"post"; nocase; content:"/";
> nocase; pcre:"/^post\s+\/\s+http\/1.1/smi";
> classtype:attempted-recon; sid:050201; rev:10;)
> i am new to snort, so i don't know if this rule is correct,
> for example, i don't know where to get a correct sid, i took
> the current date.
> what i did, i took an other smtp-rule and did modify the content.
> best regards
> hans
> p.s.: i hope this is the correct forum, or should i post
>       in the Snort-users list ?
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