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RE: POP vs IMAP vs MAPI - security through firewalls?
From: Ben Nagy <ben.nagy () marconi com au>
Date: Mon, 26 Feb 2001 13:44:44 +1030

You might like this link:

To summarise:
- I don't think any M$ stuff uses port 136 for anything at all.
- I don't think any M$ stuff uses 137/138 _TCP_ for anything. UDP is used on
these ports for all sorts of nasty, NASTY stuff that a) has nothing to do
with getting mail to work and b) is BAD to pass through a firewall.
- I can't see any reason why you'd want port 139 TCP to work, either, but I
could be wrong.

AFAIK, you _should_ only need to open port 135 for RPC and some dynamic
ports, ala KB article Q270836. This may be where they get 50000 etc, but the
recommended range is 1024 - 5000, so who _knows_ what's going on.

That doesn't help you with your security comparision, though, sorry. I
wasn't aware that _any_ of those protocols were "secure" - they're all
cleartext, for a start. 

Since all the TCP connections are _supposed_ to come from the inside
outwards, though, I don't see _too_ much exposure from the protocol level.
It's a matter of guessing which implementation is most likely to be buggy, I
suppose. Toss a (three sided) coin?

(Neater solution: Run a Citrix box outside the firewall, run the ICA client
on your SUNs and then use Citrix sessions to read mail. Solves two problems
at once.)


Ben Nagy
Network Security Specialist
Marconi Services Australia Pty Ltd
Mb: +61 414 411 520  PGP Key ID: 0x1A86E304

-----Original Message-----
From: Joseph S D Yao [mailto:jsdy () cospo osis gov]
Sent: Friday, 23 February 2001 8:36 
To: firewall-wizards () nfr net
Subject: [fw-wiz] POP vs IMAP vs MAPI - security through firewalls?

Recently, one of our firewalled sites (hosted at a military base) was
directed that they had to stand down their internal mail 
server and use
the external base mail server.  This being the US military, this will
be an MS Exchange server, and the people inside the firewall are being
directed to use MS Outlook.  [How this will run on their Suns I don't
know, but that's not my problem.]

They were told they had to use MS MAPI to read the mail, and so they
would have to open TCP ports 135-139, 50000, 50001, and perhaps others
to be named later.  They were also told that MAPI must be used because
it is "slightly more secure" than POP3 or IMAP4.

The firewall is proxying-only, which of course means 
TCP-only.  I'm not
familiar with MAPI, and of course there is no RFC describing 
it, or any
publicly available documentation of which I'm aware.

Is anyone aware of any verifiable security testing that's been done on
MAPI?  Is it in fact "more secure" than POP3 and IMAP4?  You needn't
tell me that the latter two have security vulnerabilities - I've heard
this - but details would help [I haven't collected those], 
and if there
is a comparison to MAPI that would be so much the better.  Is 
MAPI that
much better?  [It had better be, to use up 7+ ports!  ;-(]

Are there any reliable proxies for any of these protocols?

Thank you!

Joe Yao                               jsdy () cospo osis gov - 
Joseph S. D. Yao
COSPO/OSIS Computer Support                                   EMT-B
This message is not an official statement of COSPO policies.
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