Re: [FW1] SMTP Telnet

[Martin Zemljic <Martin.Zemljic@astec.si>]

 This has been discussed few months ago.

 Resume:
 You can not, if someone uses line-mode telnet (such as Cisco router can
 produce),

 If you use "ordinary" telnets, you can test the packet length and/or
 telnet-specific control codes that do not appear in pop3/smtp session. However,
 you CANNOT guess whether someone uses telnet:25 or smtp/pop3 client, especially
 if he/she uses line mode telnet. Reason: Sessions are pretty equal down to
 packet level. Plus, anyone with development tool can write his own smtp/pop3
 client.

 For testing packet length (single character per packet) and control codes you
 have to modify base.def file. Please look into archives of this mailing list,
 as far as I remember, final solution was not published.

 Martin

 PS: And why they should not do this?




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 cc:    (bcc: Martin Zemljic/ASTEC)
 Subject:  [FW1] SMTP Telnet



    [ Part 2: "Attached Text" ]



I was being ask by my manager, to see the possibility of blocking telnet
session (i.e. using a telnet software and specific port 25 or 110) into a
SMTP/POP3 server, any suggestion will be greatly appreciated.

Regards

HenryW


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