Do you know what Trojan:Win64/Sirefef.U is?
Trojan:Win64/Sirefef.U is a Trojan infection that enters computer systems that run on the 64-bit version of Windows. It is from a big multi-component family called Win64/Sirefef. This family of Trojan infections modifies your overall Internet browsing experience by changing your search results and generating a lot of pop-up advertisements. Hacked search results and annoying pop-up advertisements can lead to dangerous malware infections that seriously damage your computer system. Trojan:Win64/Sirefef.U is one of the components, that download and install other malware and then monitor malicious processes that are currently running on your computer. In other words - Trojan:Win64/Sirefef.U is a dangerous infection that you have to remove immediately.
Unfortunately, contrary to rogue antispyware infections, Trojan:Win64/Sirefef.U does not have an interface, so you cannot determine whether you are infected with the Sirefef group of Trojans unless you perform a full system scan. You could try looking for the files associated with Trojan:Win64/Sirefef.U, for example, dmserver.dll, imagedrv.dll, svcwmu.dll and others. These files allow Trojan:Win64/Sirefef.U to monitor currently running processes. What is more, it also installs another Trojan component called Win64/Sirefef.Y, compromising your system even further.
In order to remove Trojan:Win64/Sirefef.U you should invest in a legitimate antimalware tool, because removing such a multi-component infection on your own is very tricky. An automated malware removal tool will scan your system and detect every single Sirefef component that has to be erased immediately. When you delete Trojan:Win64/Sirefef.U, the security program of choice will also safeguard your computer against other possible infections.
In non-techie terms:
Trojan:Win64/Sirefef.U is a Trojan, that is one of the Win64/Sirefef components. It installs another dangerous Trojan, and contributes to the overall malicious activity that includes modifying your searches and displaying a list of pop-up advertisements. Remove Trojan:Win64/Sirefef.U with a powerful antimalware tool and protect your computer from other Trojans.