In computing, a blacklist is a basic access control mechanism that allows everyone access, except for the members of the black list (i.e. list of denied accesses). The opposite is a whitelist, which means allow nobody, except members of the white list. As a sort of middle ground, a greylist, contains entries that are temporarily blocked or temporarily allowed. Greylist items may be reviewed or further tested for inclusion in a blacklist or whitelist.

An organization may keep a blacklist of software or websites in its computer system. Titles on the list would be banned and everything else would be allowed. For example, a school might blacklist KaZaA and ICQ; other Internet services would still be allowed.

[edit] Examples

• Content-control software such as DansGuardian and SquidGuard may work with a blacklist in order to block URLs of sites deemed inappropriate for a work or educational environment.

• An e-mail spam filter may keep a blacklist of addresses, any mail from which would be prevented from reaching its intended destination. A popular technique for implementing blacklists is DNS blacklisting (DNSBL).

• Many copy protection schemes include software blacklisting.

• Members of online auction sites may add other members to a personal blacklist. This means that they cannot bid on or ask questions about your auctions, nor can they use a "buy it now" function on your items.

• Yet another form of list is the yellow list which is a list of email server IP addresses that send mostly good email but do send some spam. Examples include Yahoo, Hotmail, and Gmail. A yellow listed server is a server that should never be accidentally blacklisted. The yellow list is checked first and if listed then black list tests are ignored.

• In Linux modprobe, the blacklist modulename entry in a modprobe configuration file indicates that all of the particular module's internal aliases are to be ignored. There are cases where two or more modules both support the same devices, or a module invalidly claims to support a device.

[edit] See also

• Whitelist