3.  Nuisance viruses  Data-destructive viruses  Espionage viruses  Hardware-destructive viruses

4.  E-mail viruses  Macro viruses  Boot sector viruses  Trojan Horse viruses  Stealth viruses  Polymorphic viruses  Logic (time) bombs

5.  Files become corrupt  Program does not operate properly  Programs or files vanish  Strange messages appear on monitor  Less memory space available  A volume name has changed  E-mail message appears repeatedly

6.  Data backup  Disaster recovery plan  Data encryption  User IDs and passwords  Biometric authentication  Network sniffers  Mini webcams  Firewalls