Blacklists are blacklists or negative lists on which persons, systems, domains or websites are listed that are excluded from communicating with certain computers or services and cannot log into them. The blocked computers and people are recognized by their IP address, user ID, domain name, email address or MAC address.
In communications technology, blacklists are used to block e-mail addresses or websites with which writings harmful to minors, right-wing extremists or those glorifying violence are e-mailed or displayed on websites. Mails or websites with spam or those that send viruses or Trojans are also indexed on such negative lists. Real-time queryable blacklists that identify emails as spam are called real-time blackhole lists( RBL) and DNS-based blackhole lists( DNSBL).
A blacklist is also a list of discrete entities, such as hosts or applications, that have attracted attention for malicious activity. Doamins that are blacklisted are not indexed by search engines and should not be listed in search results if possible. The corresponding websites are identified by filters and permanently and sometimes irreversibly deleted by the search engine operators so that they do not end up in their caches again after some time.
In contrast to the blacklist is the positive list, the whitelist, in which valid certificates are entered.