Identification
Its full user-agent string, exactly as it arrives at the gate:
To check a visitor really is YandexBot, run a reverse DNS lookup on its IP address and confirm the hostname ends in .yandex.ru, .yandex.net, .yandex.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. Read Yandex's documentation.
How to block YandexBot
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 YandexBot's next visit. Nothing else on your site needs to change.
# Block YandexBot from the whole site User-agent: Yandex Disallow: /
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: Yandex Allow: / Disallow: /members/
Observed behaviour
Nothing on record in the last 30 days.
Requested 0 disallowed pages out of 0 requests. Never read robots.txt.
Has never followed the hidden link to /trap/. Either well trained or very lucky.
Where it comes from
Requests that use YandexBot's name but fail Yandex'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.
Questions site owners ask
Does YandexBot respect robots.txt?
We can't say yet. It has not fetched robots.txt here, and it has not touched a disallowed page either.
Will blocking YandexBot hurt my search rankings?
Yes, for Yandex's search engine. Blocked pages can drop out of its results. Other search engines are unaffected.
How often does YandexBot visit?
Here, about 0 requests a day over the last week. Visits to your site depend on its size, how often it changes, and how many links point to it.