RE: Blocking Outlook External POP/SMTP

[Jay Vlavianos <jvlavianos () ecastnetwork com>]

You could always look into an EIM product like Websense(tm) to manage blocking at the service level instead of the port 
level.  Things like webmail are tough to get around, especially with Exchange funneling everything over port 80/443 now 
at the CAS layer (which Outlook can use as a server source).

At the end of the day, though, an enterprising user could get around port blocking in many ways including tunneling it 
though ICMP if need be (see PingTunnel http://www.cs.uit.no/~daniels/PingTunnel/)



-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of Hart, Lee Anne
Sent: Thursday, March 11, 2010 1:41 PM
To: 'security-basics () securityfocus com'; 'firewalls () securityfocus com'
Subject: Blocking Outlook External POP/SMTP

Hello,

I'm looking for information on preventing/prohibiting users from utilizing
Outlook (at work) to retrieve their personal email from Gmail, AOL, Yahoo,
Comcast, Verizon, etc.

Looking for the following:

* Reasons why users should not be allowed to use Outlook on their work
computers to retrieve their personal email.

* Tools/techniques to block this type of traffic. It seems the most common
ports are 110, 465, 587, 993, and 995. Are there others? 

Any reference are much appreciated. 

Thank you!
Lee Anne




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