Blacklist (computing)

In computing, a blacklist, disallowlist, blocklist, or denylist is a basic access control mechanism that allows through all elements (email addresses, users, passwords, URLs, IP addresses, domain names, file hashes, etc.

Example uses include a company that might prevent a list of software from running on its network, a school that might prevent access to a list of websites from its computers, or a business that wants to ensure their computer users are not choosing easily guessed, poor passwords.

[2] An information system includes end-point hosts like user machines and servers.

A blacklist in this location may include certain types of software that are not allowed to run in the company environment.

An e-mail spam filter may keep a blacklist of email addresses, any mail from which would be prevented from reaching its intended destination.

In addition to private email blacklists, there are lists that are kept for public use, including: The goal of a blacklist in a web browser is to prevent the user from visiting a malicious or deceitful web page via filtering locally.

As expressed in a recent conference paper focusing on blacklists of domain names and IP addresses used for Internet security, "these lists generally do not intersect.

"[8][9] This concern combined with an economic model[10] means that, while blacklists are an essential part of network defense, they need to be used in concert with whitelists and greylists.