What Is A Whitelist?

Date First Published: 23rd August 2023

Topic: Cybersecurity

Security Mechanisms & Technologies

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 4/10

CONTENTS

Uses Of Whitelists

Learn about what a whitelist is in this article.

A whitelist, also known as an allowlist, or a passlist, is a list of email addresses, IP addresses, domain names, usernames, passwords, and applications that are granted access to a specific system or protocol. With the exception of those items listed in the whitelist, all other items are denied access.

A whitelist is the opposite of a blacklist, which refers to a list of email addresses, IP addresses, domain names, usernames, passwords, and applications that are denied access to a specific system or protocol. Therefore, whitelists are more suitable when most items need to be denied access and blacklists are more suitable when a limited number of items need to be denied access.

Uses Of Whitelists

Whitelists can be used in spam filters to exclude certain IP addresses, email addresses, and domain names from being moved to the junk folder. The whitelist can be manually selected by the user, but can also be maintained by the email provider. Some spam filters may be very strict and only configured to accept messages from email addresses that have been added to the whitelist.

Whitelists are also used in adblockers. Adblockers, which prevent ads from being displayed on webpages usually have a feature to whitelist certain websites and pages, which will exclude the adblocker from running on that page. Ads will display on pages whitelisted by adblockers.

Protected directories, files, and file types may use a whitelist to limit access to certain IP addresses or IP ranges. This is often used for webpages that contain sensitive information, such as personal financial data and websites under construction that should not be accessible to the public. Any visitor requesting to view a webpage, directory, or file type whose IP address or IP range is not whitelisted will be unable to view the page and may get a 403 error.

Firewalls can be configured so that only traffic coming from specific IP addresses and IP ranges is allowed. This stricter type of firewall is often used by schools, workplaces, and parental controls, to only allow access to specific sites. When added to a whitelist, an IP address or IP range is considered safe and access is granted.