Information about Whitelist

A whitelist is a list of accepted items or persons in a set. This list is inclusionary, confirming that the item being analyzed is acceptable. It is the opposite of a blacklist which confirms that items are not acceptable.

E-mail whitelists

An e-mail whitelist is a list of contacts that the user deems are acceptable to receive email from and should not be sent to the trash folder.

Spam filters that come with e-mail clients have both white and black lists of senders and keywords to look for in e-mails. If a spam filter keeps a whitelist, mail from the listed e-mail addresses, domains, and/or IP address will always be allowed.

Internet service providers have whitelists that they use to filter e-mail to be delivered to their customers. ISPs receive requests from legitimate companies to add them to the ISP whitelist of companies. Companies either pay for a time period to be allowed to e-mail their customers or the companies pay per complaint received by the ISP from their customers. These payments per complaint increase incrementally: ie. The first 10 complaints are $10 each. The next 10 are $20 each. These funds are then used by the ISPs to fund anti-spam programs to prevent unwanted e-mail.

If a white list is exclusive, only e-mail from those on the white list will get through. If it is not exclusive, it prevents e-mail from being deleted or sent to the junk mail folder by the spam filter. Usually, only end-users would set a spam filter to delete all e-mails from sources not on the white list, not internet service providers or e-mail services.

Using whitelists and blacklists can assist in blocking unwanted messages and allowing wanted messages to get through, but they are not perfect. E-mail whitelists are used to reduce the incidence of false positives, often based on the assumption that most legitimate mail will be from a relatively small and fixed set of senders. To block a high percentage of spam, e-mail filters have to be continuously updated as e-mail spam senders create new email addresses to e-mail from or new keywords to use in their e-mail which allows the e-mail to slip through.

Note: Whitelisting can sometimes be perceived as a derogatory term; racially charged. Whitelisting and blacklisting are also referenced as "safe senders list" and "blocked list".

Commercial whitelists

Commercial whitelists are a system by which an internet service provider allows someone to bypass spam filters when sending e-mail messages to its subscribers, in return for a pre-paid fee, either an annual fee or a per-message fee. A sender can then be more confident that his messages have reached their recipients without being blocked, or having links or images stripped out of them, by spam filters. The purpose of commercial whitelists is to allow companies to reliably reach their customers by e-mail.

Commercial providers include Habeas' Safelist, Sender Score Certified (formerly Bonded Sender), SuretyMail (formerly ISIPP IADB), and GoodMailSystems's Certified Email.

LAN whitelists

Another use for whitelists is local area network (LAN) security. Many network admins setup MAC address whitelists or a MAC address filter to control who is on their networks. This is used when encryption is not a practical solution or in tandem with encryption. However, it's sometimes ineffective because a MAC address can be faked.

Program whitelists

If an organization keeps a white list of software, only titles on the list will be accepted for use. For example, a school might whitelist MATLAB and Netscape Navigator, thus allowing only those programs to be used on its computers. The benefits of whitelisting in this instance are that the school administration can ensure itself that students will not be able to download and/or use programs that have not been deemed appropriate for use.

Anti virus whitelists

An emerging approach in combating viruses and malware is to whitelist software which is considered safe to run, blocking all others. Some deem this as superior to the standard anti-virus approach of blocking/removing known harmful software (essentially blacklisting), as the standard approach generally means that exploits are already in the wild. Criticisms of this approach often state that the list of acceptable software is substantially larger than the list of malware, making centralized application list management approaches unwieldy.

To overcome the cumbersome overhead associated with generating and maintaining a global whitelist, new approaches using self-learning whitelists have been found to be effective and to provide management efficiencies. Information asssurance techniques such as Malware Spread Mitigation employ self-derived key generation which eliminate the reliance on centralized application approval databases.