A whitelist is list of administrator-approved entities including IP addresses, email addresses and applications.
Items on a whitelist are granted access to the system allowing them to be installed, altered, and communicated with over the private's network. The goal of having a whitelist is to protect a private network and its devices from outside attacks.
Whitelisting is the direct opposite of blacklisting. The two are cybersecurity strategies that manifest as policies where administrators have explicitly sanctioned or have prohibited domains and locations they have deemed safe or unsafe. Whitelisted locations would be subject to normal visitation and usage. A blacklisted location or service would be impossible to access through admins' technical enforcement against the action.
Rather than take an exhaustive approach to adding items to a whitelist, the default approach of granting access to everything is generally applied and when there is evidence or suspicion that an IP address, domain, service, or application is unsafe, admins blacklist it.
"Our university admin keeps a long whitelist of students and faculty users who are able to access systems after hours."