Is there a list of known proxy servers (IP addresses) to bypass a firewall's access rules?

Most firewalls make it easy to exclude specific IP addys and ranges. You just want to make a rule that closes all outbound traffic to those destinations. Dont just close 80 or they'll go out another port.

I'm a professional security consultant and have been working with firewalls and business security for many years. I'm not a fan of Sonicwalls (Astaro is my preference), but nevertheless the problem you're facing is one that many businesses face every day -- how to deal with users that try to circumvent firewall rules. The usual reaction is to try to find a technical solution -- and that may work for a little while until the users find some other way around the new fix. I think you need to take 3 steps back and realize that you're dealing with more of a HUMAN problem than a TECHNICAL one. What you need is a company-wide security policy -- something solidly backed by management -- that lets employees know the rules of the road and spells out that Internet abuse will not be tolerated and may result in getting fired. Employees should sign an Internet usage agreement, and know that their Internet usage is subject to monitoring. Hope this is helpful to you.