A user reports that their computer has started to display frequent antivirus alerts stating that their system is infected with multiple viruses and that they need to pay for premium software to remove these infections. These alerts began appearing after the user installed a new 'performance optimization' program from a web advertisement. Given this information, what is the BEST action the user should perform first to address this situation?
Uninstall the recently installed 'performance optimization' program from the computer.
Update the antivirus definitions and then run a full system scan.
Purchase the premium version of the software being advertised by the alerts to remove the infections.
Immediately run an antivirus scan with the currently installed antivirus software.