While many services maintain lists of Internet Protocol addresses that are banned from accessing those services, there is no overarching blacklist of banned IP addresses that is applied to the entire Internet. However, certain ranges of IP addresses have been reserved for use on internal networks or for other special purposes and cannot be used as valid IP addresses over the Internet.
Many domains ban certain IP addresses or ranges of IP addresses for several reasons, including abuse of the services provided by that domain or associations with fraud or spam email. For example, some system administrators block most or all IP addresses associated with countries such as Nigeria, due to the large amount of spam email produced from that country. There are services that provide compilations of such email addresses in ready-made blacklists for use by system administrators, but the composition of these lists varies from provider-to-provider.
Reserved IP addresses are not banned in the sense of most usages of the term, but are restricted from use on the wider Internet due to conventions of the IP addressing system. For example, the IP 127.0.0.1 is reserved for the "loopback" interface on a computer and redirects Internet traffic back to the originating computer. Similarly, addresses in the 192.168.0.0 range are reserved for addressing computers in local networks.