There are two main types of security software:
Security software packages:
These are full security packages that provide virus scans and other protection including a firewall, spam filtering and parental controls. Good quality free security software is available from many providers for computers and mobile devices, with an option to upgrade for additional functionality and technical support.
Antivirus / Antispyware scanners and malware removal software:
These scan your computers or mobile devices for existing infections and remove them. They can usually be set to check your system on a regular basis. As computers can appear to function normally when infected, it is a good idea to run these regularly in addition to installing antivirus software
(Text courtesy of www.Cyberstreetwise.com)