thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Commonly confused · Application & OT Security

Allow List vs Deny List: What's the Difference?

An allow list permits only explicitly approved items and blocks everything else (default deny). A deny list blocks known-bad items and permits everything else (default allow). Allow lists are more secure but harder to maintain.

Allow List

vs

Deny List

Allow ListDeny List
Default actionDenyAllow
Unknown itemsBlockedPermitted
Security strengthStronger, stops unknown threatsWeaker, misses new threats
MaintenanceHigh, must approve every new itemLower, but constantly chasing threats
ExamplesApplication allow listing, firewall implicit deny, input validationAntivirus signatures, blocked domains, banned passwords
Older termsWhitelistBlacklist
Remember it

Allow lists trust no one new; deny lists trust everyone not yet caught.

Exam tip

For hardening kiosks or critical servers, application allow listing is the strongest answer. For input validation, allow listing is preferred over deny listing.

Tested on

More Application & OT Security look-alikes