MCP & Tooling
Allowlist and Denylist
Also: allow list, deny list, blocklist
Two ways to filter actions: an allowlist permits only what is named, a denylist blocks only what is named.
In more detail
Allowlists are safer because anything new is blocked by default, but they take more upkeep. Denylists are easy to start and easy to bypass, since attackers can use a command or host nobody listed. For agents, use allowlists for network egress and high-risk tools, and denylists as a supplementary layer for known-bad patterns.
