A personal firewall differs from a conventional firewall in terms of scale. Personal firewalls are typically designed for use by end-users. As a result, a personal firewall will usually protect only the computer on which it is installed.
Many personal firewalls are able to control network traffic by prompting the user each time a connection is attempted and adapting security policy accordingly. Personal firewalls may also provide some level of intrusion detection, allowing the software to terminate or block connectivity where it suspects an intrusion is being attempted.