blocking hotmail and yahoo.com in ASA 5510

Posted on 2009-05-05
Medium Priority
Last Modified: 2013-11-16
Question by:alimohammed72
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LVL 33

Expert Comment

ID: 24304525
In an ASA Firewall you can block any outbound request using an Access list.   THE ACL is read in sequential order, top to bottom, so as soon as there is a match the processing stops.  

Your list would need to look something like this:

Access-list inside_to_outside extended deny ip any <ip address subnet of hotmail>  <subnet mask of hotmail>
Access-list inside_to_outside extended deny ip any <ip address subnet of yahoo>  <subnet mask of yahoo>
Access-list inside_to_outside extended permit tcp any any eq 80
Access-list inside_to_outside extended permit tcp any any eq 443

access-group inside_to_outside in interface inside

This will block any ip request to the ip subnet of hotmail or yahoo yet allow any other port 80/443 request outbound.   There is an implicit deny at the end of any access list, so all other communication would be blocked.  


Author Comment

ID: 24305488
how am I going to know the subnets for Hotmail and Yahoo
LVL 33

Accepted Solution

MikeKane earned 2000 total points
ID: 24305813
Here are the hotmail ips

Here are the yahoo ips

You know that anyone can still hit a public proxy then get to these sites....     Or setup a personal proxy at home and bypass this ip range.      The best way to block this would be setup a web filter like websense and block the webmail category along with the proxy/anonymizer category.  


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