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Funny SMTP

These are a few real SMTP conversations. Unfortunately, all these machines do either no longer exist or no longer react like that. As you can see, the system administrators of the respective systems had once had too much time at their hands (or just needed to blow some steam). They also knew that some people were really using the text interface, e.g., for debugging.

You can also see the use of continuation lines, which haven't been discussed in class, such as the

220-
lines preceding the final
220 
line.

Hitchhiker's Guide to SMTP

Last known to work in April of 1996:
% telnet mail.germany.eu.net smtp
Trying 192.76.144.65 ...
Connected to mail.germany.eu.net.
Escape character is '^]'.
220-mail.Germany.EU.net - EUnet gateway to Germany
220 ESMTP spoken here
EHLO nice.ethz.ch
250-mail.Germany.EU.net Hiya nice.ethz.ch [129.132.66.13], long time no see
250-SIZE 20000000
250 HELP
MAIL from: waldvogel@nice.ch SIZE=335
250 waldvogel@nice.ch... A real hoopy frood.
[...]
.
250 QAA01569 Message accepted for delivery
RSET
250 Reset state: 38911 BASIC BYTES FREE.
QUIT
221 So long, and thanks for all the fish.                                       

Hacker-friendly SMTP server

Again the same machine (this part is thanks to Daniel "Clüsch" Kluge). To understand the humor behind this, you should be aware that many of the break-ins into computers occured by taking advantage of bugs in sendmail, the most popular mail transfer agent (MTA). Probably the most prominent example is the so-called Morris Worm of 1988, but there have been many more security incidents relying on sendmail. Also, several of the commands have been documented in the HELP text for ages, but never worked.
% telnet mail.germany.eu.net smtp
Trying 192.76.144.11... Connected to mail.germany.eu.net.
Escape character is '^]'.
220-mail.Germany.EU.net - EUnet gateway to Germany
220 ESMTP spoken here
help
214-Commands:
214-    HELO    EHLO    MAIL    RCPT    DATA    RSET
214-    NOOP    QUIT    HELP    VRFY    EXPN    VERB
214-Not implemented:    TURN    SOML    SAML    SEND
214-Non standard:       SHEL    WIZ     DEBUG   KILL    TTY     PTY
214-
214-For more info use "HELP <topic>". Bug reports to mail@Germany.EU.net.
214-
214-Whence camest thou, Worthy Thane ?
214-From Fife, Great King, where the Norwayan banners flout the skye
214-and  fanne oure people colde.
214 End of HELP info
help wiz
214-WIZ <password>
214-    Pretend to be a wizzard.
214 End of HELP info
help kill
214-KILL
214-    Nuke the initiator of this command.
214 End of HELP info
help tty
214-TTY
214-    Become attached to a terminal. Useful in preparation for a
214-    subsequent SHEL command. Same as PTY in this implementation.
214 End of HELP info
help pty
214-PTY
214-    Become attached to a terminal. Useful in preparation for a
214-    subsequent SHEL command. Same as TTY in this implementation.
214-    Note:
214-    ===== Becoming attached to a terminal (as opposed to another
214-          human being) may be dangerous to your health.
214-          Consult your shrink.
214 End of HELP info
help shel
214-SHEL
214-    Same as SHEL in this implementation.
214 End of HELP info
help soml
214-SOML FROM: <sender>
214-    Specifies the sender. Send to terminal of a user or mail.
214-    Never was, nor ever will be, implemented.
214 End of HELP info
help saml
214-SAML FROM: <sender>
214-    Specifies the sender. Send to terminal of a user and mail.
214-    Never was, nor ever will be, implemented.
214 End of HELP info
help send
214-SEND FROM: <sender>
214-    Specifies the sender. Send to terminal of a user, do not mail.
214-    Never was, nor ever will be, implemented.
214 End of HELP info
quit
221 So long, and thanks for all the fish.

Forging "Prevention"

Many people used the direct text interface to fake senders (nowadays, there are simpler options; anyway, someone knowledgeable looking at the mail headers can typically find many clues to who sent or didn't send the mail). The following dialog refers to that. Thanks to Thomas Andres, we know that even the reputable Swiss bankers do sometimes show a sense of (sometimes rather weird) humor.

Update (2005-03-01): I received an email from that bank's security incident response team manager requesting me to remove the bank's name from this URL. (The IP address no longer belongs to them, so it does not leave any identifying marks.) It seems that current management no longer approves the former sysadmins' humor. I am not sure how this relates to security incidents, however...

% telnet mail.<major-swiss-bank>.com 25
Trying 194.209.128.98...
Connected to mail.<major-swiss-bank>.com.
Escape character is '^]'.
220 unigate1 SMTP ready, Who are you gonna pretend to be today?
HELO blabla.microsoft
250 unigate1 Is thrilled beyond bladder control to meet blabla.microsoft
MAIL FROM: sten@ergon.ch
250 sender is sten@ergon.ch, (yeah sure, it's probably forged)
RCPT TO: gunterberg@ergon.ch
250 recipient bounce.me@<major-swiss-bank>.ch, I know them! they'll just *LOVE* to hear from you!
DATA
354 OK, fire away. End with <CRLF>.<CRLF>
From: sten@ergon.ch
To: bounce.me@<major-swiss-bank>.ch
Subject: mail test

bla bla
.
250 Whew! Done! Was it as good for you as it was for me?
quit
221 It's been real. Take off Eh!

More...

You can find two more in here (search for "helo"). But don't spend too much time reading through the messages in there and their friends.

Copyright 2000-2004 Marcel Waldvogel