How does a firewall keep out intruders?
Information flows over networks in “packets”. Packets are groups of characters sent from one device to another. Each packet has the “address” of the machine it is intended for and the address of the originating computer. Special computers, called routers, pass the packets from the originating computer to the destination computer. When a destination computer sees a packet with its address, it opens to packet to get the characters or bytes. The trouble is, any computer can send packets to any computer on the internet. Hackers take advantage of this to hack into computers. The firewall sets itself up as a visible location on the internet. The computers on your network are not visible from the internet. When one of your computers asks for something from the internet, the firewall changes the originating computer address in the packets to its own address. When the response comes back to the firewall via the internet, it examines the packet then forwards it on to your computer. If a packet c
