Trojan:Win32/Medfos.A is a trojan that attempts to download arbitrary files from websites such as "greatfilehosting.com" and "midifilehosting.com".

Microsoft security software detects and removes this family of threats. 

These threats install malicious Internet browser extensions and redirect your search results. This means that if you search using Google, Bing, or Yahoo, for example, the site returns normal search results. However, if you click on any of the results, instead of going to the correct website, you might be redirected to a different website.

These threats can also be used for click-fraud.

Variants of Win32/Medfos can be installed by other malware, including variants of the Trojan:Win32/Necurs family.

Find out ways that malware can get on your PC.

Windows Defender detects and removes this threat.

This family of threats are malicious JavaScript files that redirect web searches to pay-per-click advertising sites.

This threat might be installed on your PC from a Win32/Medfos variant.

Find out ways that malware can get on your PC.