Blocking content coming into and going out to the Internet. Accomplished by firewall software residing in a stand-alone device, router or user's machine, or in a filtering program in each user's machine, content can be blocked by website or Internet service. For example, users might be allowed access to the Web but not to file transfers (FTP). Websites and Internet Services websites and Internet services can be blocked for specific users or for all users. Blocked websites are identified by their Web address (URL), by words in their address or by domain (.com, .edu, etc.). Identified by their TCP/IP port number; for example, Web traffic is port #80, Internet services can be blocked as a complete group such as the entire Web, all e-mail and all file transfers. In the home, parents can restrict their children's access with special browsers and filtering programs (see parental control software).