The computer virus is an outcome of the computer overgrowth
in the 1980s. The cause of this term is the likeness between the
biological virus and the evil program infected with computers. The origin of
this term came an American science fiction "The Adolescence of P-1" written
62. ______ by Thomas J. Ryan
published in 1977. Human viruses invade a living cell and turn them into a
factory for manufacturing viruses.
63. ______ Therefore, computer
viruses are small programs. They replicate by attaching
64. ______ a copy of themselves to another program.
Once attached by host program, the viruses then look for other programs
65. ______ to" infect". In this way, the
virus can spread quickly throughout a hard disk or an entire organization. At
some points, the situation will be 66.
______ totally determined by how the virus was programmed. The timing of
the attack can be linked to a number of situations, included a certain time
67. ______ or date, the
presence of a particular file, the security privilege level of the user and
the number of times a file is used. So-called" benign" viruses might simply
display a message, like the one that infected IBM’s main computer system last
Christmas with a season’s greeting. Malignant viruses are designed to damage
the system. The attack is to wiping
68. ______ out data, to delete files or to format the
hard disk. There are two main types of viruses: shell and
intrusive system. Shell viruses wrap themselves around a host program and
don’t modify the original program. Shell programs are easy to write, that is
why about 69. ______ half of viruses
are of this type. Intrusive viruses invade an existing program and actual
insert a portion of themselves into the host program.
70. ______ Intrusive viruses
are hard to write and very difficult to remove with
71. ______ damaging the host file.