IP level security is straightforward (see Figure 6.7). You can grant access to all computers except for those with specific IP address, or you can deny access to all computers except for those with specific IP addresses. Securing a system at the IP level can provide an extremely high level of security, but it is a double-edged sword. You can inadvertently lock out the general public, which is not consistent with World Wide Web practices. Likewise, security is difficult to test. You cannot test whether unauthorized people have gained access to a system unless you catch them as they come in.