Disconnect the computer from the internet
Unplug external drives and USB devices
Boot into Safe Mode
Run a full scan with your antivirus software
Update your antivirus definitions first if possible
Run a second scan with a trusted anti-malware tool
Quarantine or delete any detected threats
Uninstall suspicious programs
Remove unknown browser extensions and add-ons
Clear temporary files and browser cache
Check startup programs and disable suspicious entries
Review installed apps for anything unfamiliar
Restore browser settings to default
Change important passwords from a clean device
Enable two-factor authentication on important accounts
Update the operating system and all software
Restore from a clean backup if needed
If the infection remains, back up important files and reinstall the operating system