Limitations
• The firewall cannot protect against attacks that bypass the firewall.
• The firewall may not protect fully against internal threats, such as a disgruntled employee or an employee who unwittingly cooperates with an external attacker.
• An improperly secured wireless LAN may be accessed from outside the organization. An internal firewall that separates portions of an enterprise network cannot guard against wireless communications between local systems on different sides of the internal firewall.
• A laptop, PDA, or portable storage device may be used and infected outside the corporate network, and then attached and used internally.