Application whitelisting uses the reverse logic. Here, you can create a list of trusted entities such as applications, emails, users, trusted partners, services and IPs. These are allowed to access IT resources and block everything which seems to be unwanted for your business. With whitelisting architecture, you must have a tight access control policy and grant appropriate permission to users. Since you block all unwanted entities, this reduces the attack surface which gives automatic protection from zero-day attacks.