A boot sector virus replaces the program used to start the system with a modified version of the program. A file virus inserts virus code into program files. A Trojan horse virus hides within or is designed to look like a legitimate program. A macro virus uses the macro language of an application to hide virus code. Virus Detection and Removal A ntivirus programs , called vaccines , have been developed to protect against computer viruses.
Vaccines look for specific patterns of virus code called a virus signature .
Antivirus programs have utilities to remove or repair infected programs and files. A rescue disk is a floppy disk that contains an uninfected copy of certain operating system commands and essential information that enables the computer to restart correctly. Unauthorized Access and Use U nauthorized access is the use of a computer system without permission. Crackers , or hackers , are people who try to access computer systems illegally. Unauthorized use is the use of a computer system or computer data for illegal or unapproved activities.