Apologies if this is overly paranoid.
I recently discovered the Wolfram Demonstrations Project and intend to play with them to understand some of the power of Mathematica.
I have one slight concern: given that Mathematica has all types of system access, what guarantees do I have about these demonstrations (i.e. that they don't maliciously modify my file system, steal ssh keys, install trojans, etc ... )
I would prefer an answer of the form: "option XYZ lets you disable all of that for specific notebooks" rather than an answer of the form "everyone loves each other and would never do that!"