What is trojan horse vundo.jl?

It is a trojan that contain backdoor functionality that gives an unauthorized user access to an affected machine. They have been ociated with adware. Try to download Malwarebytes from their website and install it on your system. Do an update and when it's done. Click on "Perform Quick Scan". When it's done, click view results and select remove selected items if there's some. You may have to disable or remove any peer-to-peer programs like BitTorrent which is a know source of malwares. Message me if it's not removed yet.