Scan for viruses and other malware
Its obviously you have a virus scanner installed, but it is also up to date? If you do not have a virus scanner find a free one free virusscanner install it and make sure its up-to-date. However never install two viruscanners on your PC, then you’re asking for trouble. If you doubt you can still do an extra scan with a free online-scanner and preferable a other one then the one you have installed.