A system identifies undesirable content in responses sent to a user, such as in e-mail or in downloadable files, from an Internet or intranet site. The system utilizes a redirection program that identifies content requests from a user to a target server. The redirection program redirects the request to a proxy server that sends the request to the target server. Upon receipt of the response from the target server, the proxy server scans the response, which includes any attachments, for undesirable content, such as junk e-mails, computer viruses, pornographic material, and/or other undesirable content. The proxy server then acts upon the response, and any undesirable content, in accordance with default or user-defined parameters, such as removal of the undesirable content. The proxy server may then send the response, as modified, or a notification message to the redirection program forwarding to the user.