denoland-deno/docs/getting_started/permissions.md

Permissions

Permissions whitelist

Deno also provides permissions whitelist.

This is an example to restrict file system access by whitelist.

$ deno run --allow-read=/usr https://deno.land/std/examples/cat.ts /etc/passwd
error: Uncaught PermissionDenied: read access to "/etc/passwd", run again with the --allow-read flag
► $deno$/dispatch_json.ts:40:11
    at DenoError ($deno$/errors.ts:20:5)
    ...

You can grant read permission under /etc dir

$ deno run --allow-read=/etc https://deno.land/std/examples/cat.ts /etc/passwd

--allow-write works same as --allow-read.

This is an example to restrict host.

const result = await fetch("https://deno.land/");

$ deno run --allow-net=deno.land https://deno.land/std/examples/curl.ts https://deno.land/