Make sure your computer's operating system is patched with the latest security updates provided by the manufacturer.
Spyware can accumulate on a system just by browsing the web. Systems should be checked for spyware no more than every 30 days. CIS recommends Spybot Search & Destory and Malwarebytes Anti-Malware for spyware-removal.
Separately from spyware scans, users are required to run active anti-virus software that is constantly running on a system. More information can be found on the AntiVirus page.
In addition to both Antivirus and Spyware removal software, a personal firewall is required on all systems. Firewalls are provided by default on all Apple Mac OS and Microsoft Windows computers.