Please keep in mind that no servers are allowed to run on Insight's network.

What is an open proxy?
An open proxy is a server that acts as an open relay but uses ports other than the normal SMTP port 25. Open proxies provide surrogate (proxy) communication ability to other servers or PCs through ports not reserved for normal use. There are many viruses and Trojans that can be used to install open proxy software on an unsuspecting user's computer. This is the most common usage of a proxy on a cable modem network. Spammers regularly use these types of servers to disguise the true origin of their unwanted e-mail. In recent months spammers have even joined forces with virus writers to develop more robust Trojans and viruses to be used solely for the purpose of sending spam. If you have received an notification (via e-mail, postal mail or Internet block message) from Insight's Fraud and Abuse Security Team about spam e-mail then it's likely that spammers have indeed located and exploited your unsecured PC for this very reason.

Why should I secure my open proxy?
This is a similar situation to running an open relay: you are allowing non-paying users on the Internet to have free rein of your resources. Most of the open proxies that we see have been installed by viruses or Trojans. Most of the people we've worked with are not aware of their vulnerabilities. Failure to resolve this type of situation may result in your IP address, or that of an Insight mail server, being "Black Listed" preventing you or possibly a large number of Insight's customers from being able to send mail to others on the Internet.

How do I secure my open proxy?
You can disable connections to the open ports in question, establish an access-control-list (ACL) to only allow certain users on your system or use a personal firewall. For more detailed instructions, please consult your operating system's vendor support line or your local PC support personnel.

Checking for an open proxy yourself
You can test your firewall security by doing a remote scan of your system from Shields UP!! by Gibson Research (http://grc.com)

On which ports am I vulnerable?
Common proxy ports are listed below. If you run netstat -an and see connections to these ports on your PC then there is something running and most likely it is a proxy. Proxies are not limited to these ports but are most commonly found in these port ranges: 80, 81, 8000, 8080 (HTTP CONNECT), 1080 (SOCKS), 3128 (Wingate/Squid), 6588 (AnalogX).

NOTE: This is only a list of common ports. Others can be used for the same purposes but are less common.

What if I have done all of the above suggestions but haven't found anything wrong?
Your system(s) are likely infected with some type of virus or Trojan. We recommend that you ensure that your anti-virus software is completely up to date and that you do a full system scan. We also recommend using anti-Trojan software to locate and remove any Trojan software that may be residing on your system(s). Trojan software is the most common cause of an open proxy and may also allow someone complete control of, and access to, your system(s) without your knowledge. If you do not locate anything with one anti-Trojan software package you may wish to try another. Many of these programs are specialized and will not pick up all Trojans that exist on the system.