Yet Another Recursive/Ridiculous Acronym (YARA) is a multi-platform tool for matching patterns of interest in malicious files. It was created by Victor Alvarez from VirusTotal. It is used to perform research on malware families and identify malware with similar patterns. It can help in categorizing malware in different malware families, and can also be used as a detection aid for malware analysis.
There are various open-source repositories of Yara rules shared by different organizations and people that can be leveraged by the security community in their fight against malware. This GitHub repository contains links to a lot of such open-source repositories.
This was a fairly easy exercise based on Day 20. I recommended reading this link once to answer the last 2 questions.
