Mediapartners-Google

Its full user-agent string, exactly as it arrives at the gate:

To check a visitor really is Mediapartners-Google, run a reverse DNS lookup on its IP address and confirm the hostname ends in .googlebot.com, .google.com, .googleusercontent.com. Then run a forward lookup on that hostname and check it returns the same IP. Anything that fails is an impostor; the zoo checks every visit this way and files the failures in the Trap Room.

Add these two lines to the robots.txt file at the root of your site. Well-behaved crawlers read it before they crawl, so the change applies from Mediapartners-Google's next visit. Nothing else on your site needs to change.

# Block Mediapartners-Google from the whole site
User-agent: Mediapartners-Google
Disallow: /

If your site shows AdSense ads, do not block it. Without it, AdSense cannot read your pages and ads become less relevant.

Or let it visit but keep it away from part of the site:

# Let it in, but keep it out of one room
User-agent: Mediapartners-Google
Allow: /
Disallow: /members/

Requests that use Mediapartners-Google's name but fail Google's network check are filed separately, as impostors. These are the visits that passed, or that could not be checked at the time:

Nothing on record in the last 30 days.

Networks and countries come from the visitor's IP address, looked up in a local copy of the DB-IP database. The addresses themselves are never stored.