This is especially dangerous since many sites have strong firewall protection, but almost no protection against attacks from the inside. If enforced properly, this rule stops any network probing by applets. Netscape Navigator 2.0 did not enforce this rule properly. In order to understand what went wrong, you need to understand how machines are named on the Internet. Like people, machines on the Internet need to have names to identify them.
Specific names help machines send messages across a network.
These names are also numeric addresses. Because these numbers are often difficult to remember, there are two layers of network addressing in the Internet. An IP address is just a number. IP addresses are often written in decimal form, which looks like 206.26.48.100. When the computers that make up the Internet talk to each other, they identify themselves with the numeric IP addresses.