Identification
Its full user-agent string, exactly as it arrives at the gate:
There is no operator to verify against. This name is what software calls itself when nobody gave it one.
No operator stands behind this name, so there is nothing to check its visits against.
How to block MicrosoftPreview
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 MicrosoftPreview's next visit. Nothing else on your site needs to change.
# Block MicrosoftPreview from the whole site User-agent: MicrosoftPreview 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: MicrosoftPreview Allow: / Disallow: /members/
Observed behaviour
Most active around 23:00. After dark, like a burglar.
Requested 33 disallowed pages out of 33 requests. Never read robots.txt.
Has never followed the hidden link to /trap/. Either well trained or very lucky.
Where it comes from
Scripts and scanners run from wherever their owners rent a server. These are the networks behind the visits on file:
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.
Keeper's field notes
Questions site owners ask
Does MicrosoftPreview respect robots.txt?
No. It has never requested robots.txt here, and it has fetched disallowed pages 33 times.
Will blocking MicrosoftPreview hurt my search rankings?
No. Nothing respectable will miss it.
How often does MicrosoftPreview visit?
Here, about 5 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.