|Anti-spam technique: DNS blacklists|
|Date of first use:||about 1997|
|Effectiveness:||High to Low|
|Difficulty of implementation:||Medium|
|Harm:||Low to High|
DNS blacklists publish lists of IP addresses that share an undesirable characteristic. The characteristic is most often a history of sending spam, but lists also exist that include IP addresses whose owners assert they shouldn't be sending mail, addresses in a geographic region, hosts that are believed not to conform to relevant RFCs, and a wide range of other criteria.
The technical operation of DNSBLs is decribed at Description_of_DNSBLs.