It’s usually a virus on your own computer. Or a virus on a computer that is on your LAN. Scan with secondary antivirus, disable DCOM (as below) and run Malwarebytes. Do so in safe mode and in normal mode on any machines attached to your LAN.
Check your keygens, cracks and ISO’s first and foremost.
Disable DCOM
1.Go to Start > Run, type ‘regedit’ and hit Enter
2.Go to HKEY_LOCAL_MACHINE\Software\Microsoft\OLE
3.Change the value of EnableDCOM from Y to N
4.Restart Windows