Abstract: Security systems for computers connected to networks transmitting packets are disclosed. One disclosed system includes a security agent and a local security device featuring a network hardware connector, a computer hardware connector, a flash memory and a microprocessor to perform a software instruction. The security agent closes the security device by altering a setting of a bit of the flash memory. Further disclosed is a firewall on a single chip for providing security to a network transmitting packets. The firewall includes a network hardware connector, a memory for storing a rule and a software instruction for examining each packet and a microprocessor. Preferably the rule is configurable by a user and the memory includes at least one displayable Web and Web server functionally for serving a Web page and accepting a command from a user such that said at least one rule is determined by the command.