A family of Microsoft word processing software products for creating web, email, and print documents.
The Similarity checker appeared in my Word version 2402 before doing an update, indicating that the fix was on Microsoft's servers and not in the client software.
In both 2402 and 2403, I fed it the text of Lincoln' Gettysburg Address. It picked out three sentences from the middle of the speech and claimed that "32% of your text is similar to online sources". The famous "four score and seven years ago" was left untouched, as was "of the people, by the people, for the people". Fail.