topic Re: Block Proxy Avoidance Sites in Network Security

Block Proxy Avoidance Sites

smartin — Sun, 10 Mar 2019 11:38:22 GMT

ASA5520 with ASA-SSM-20. Currently using Websense product for Web filtering. Need to find a way for Firewall/SSM to track/block users using from using outside proxy servers using public IP address on port 80.

Re: Block Proxy Avoidance Sites

Farrukh Haroon — Thu, 28 May 2009 07:04:34 GMT

For tunnelling applications or web traffic? If applications, then they are most probably using the HTTP CONNECT Method, there is a signature built into the Cisco IPS for that. You can set the action to Deny for that signature. But test it out before :). Also exclude your genuine proxy servers from this signature using Event Action Filters.

Regards

Farrukh

Re: Block Proxy Avoidance Sites

Christopher Bell — Thu, 28 May 2009 09:57:00 GMT

Is there a legitimate way of doing this for those who are tunneling HTTP traffic to avoid Websense? Obviously you can block the proxy sites in Websense, but there are so many new ones every day...

Re: Block Proxy Avoidance Sites

Farrukh Haroon — Thu, 28 May 2009 13:10:04 GMT

Well you can use an ACL to block all outgoing traffic on port 80/443 EXCEPT when its sourced from your proxy servers?

Regards

Farrukh

Re: Block Proxy Avoidance Sites

Christopher Bell — Thu, 28 May 2009 16:41:43 GMT

We arn't using proxy servers. We need a way for the IPS sensor to report that someone is using an outside proxy... maybe some sort of long URL warning?

Re: Block Proxy Avoidance Sites

smartin — Thu, 28 May 2009 16:45:14 GMT

Add this statement to your ASA.

filter url http 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0 allow proxy-block

Re: Block Proxy Avoidance Sites

Farrukh Haroon — Fri, 29 May 2009 13:17:07 GMT

Do you really think this will block 'proxy avoidance sites'? Or just the proxies users put in their browser's?

Regards

Farrukh

Re: Block Proxy Avoidance Sites

smartin — Fri, 29 May 2009 13:42:17 GMT

In my case Websense was able to block these sites & the ASA command seems to be blocking IP address's when a user tries to bypass Websense when adding the IP address in IE.