The free version of the cloud based second opinion anti-malware scanner program Zemana AntiMalware (this is a direct link to download the free version because the main page links to the trial version instead of the free version, and the link to the free version used to be hidden at the bottom of that page).
What is it about?
This is how Wikipedia describes this program:
In 2015, Zemana presented an anti-malware security solution for Microsoft Windows  named Zemana AntiMalware.
It is a second opinion malware scanner designed to scan and clean a PC from malware.
It protects users from known and yet-to-be-born threats such as viruses, trojans, rootkits, computer worms, spyware, ransomware.
Zemana AntiMalware is very efficient in adware removal especially for many hard to remove adware infections.
It is a cloud based anti-malware software with its own signature database.
Zemana AntiMalware is highly optimized and lightweight with virus definitions stored in the cloud not cluttering up PCs’ drive.
Because it scans the files in the cloud, the detection time for new virus outbreaks is reduced.
In July 2016, MRG Effitas, a UK-based independent IT security research company, conducted a comparative analysis of Zemana AntiMalware and other prevalent generic ransomware tools.
The tested version of Zemana AntiMalware was 18.104.22.168.
Besides the default settings used, Pandora Cloud-Sandbox Technology was turned on.
They tested ransomware protection tools against eleven different ransomware, which have been prevalent in-the wild over the past 3–4 years.
Based on this report, Zemana AntiMalware proved to be the best ransomware protection among the tested products during the test.
Zemana AntiMalware is available in two versions, where one is for free use with limited security features and the other version is available in a form of a 14-day free trial of the commercialized version including all security features: real-time protection, bootkit and rootkit removal, ransomware protection, malware removal, browser cleaning, zero-day malware protection, malware scanning and automatic updating.