Computer
Security
Introduction
Computer security is the ability of a
system
to protect information and
system
resources.
The main objective of computer security
is
protection of information and property
from
theft, corruption, or natural
disaster, while allowing the information
and
property to remain accessible and
productive to its
intended users.
Computer
Viruses
computer virus is a malicious program
that
attaches itself to computer
systems
and destroys or corrupts data.
A computer virus is a man-made
program
or code that can attach itself
(usually
without the user's consent) to
either
another program or a file.
As this file travels to other computers, it
spreads the infection.
Spread
of Viruses
Network file system (file sharing)
Internet download
Removable media
Attachments from emails
i.
Boot-sector virus
ii.
File virus
iii.Multipartite virus
iv.Macro virus
v.
Logic bomb
Types of Computer
Viruses
Boot-sector
virus
The boot sector is that part of the OS
containing
most of the instructions for
booting
or powering up the system.
The boot-sector virus replaces these
boot
instructions with some of its own.
Once the system is
turned on, the
virus
is loaded into the main memory
before the operating
system
File
virus
File virus attaches itself to
executable
files (.exe) – those that
actually
begin a program.
When infected file or program is
run, the virus starts working,
trying
to get into main memory
and infecting other
files
Multipartite
virus
Multipartite virus infects both files
and
boot sectors, which
makes it
better
at spreading and more
difficult
to detect.
The multipartite virus
is
polymorphic virus, which can
mutate
and change form just as
human virus can.
Macro
virus
Infect documents
(files) through
the macro programming
capabilities
of some programs.
They are embedded inside
common
data files, such as those
created
by e-mail or
spreadsheets,
which are sent over
computer networks.
Macro
viruses become active
when
an infected document is
opened, and the program
opening
the document has its
macro
capabilities turned on
(enabled).
Logic
bombs
Logic bombs, or simply bombs,
differ
from other viruses in that
they
are set to go off at a certain
date
and time.
Many programmers set
the
malicious
virus off during days
such as April Fools
Day.
Damages
by Viruses
Deletion of data or
programs
Reformatting of hard
disk
Modify data
Introduce typing errors
Replicating and filling
up the disk
space
Why
Creating Viruses?
Intellectual challenge
To relieve boredom
Revenge
Economic reasons
Virus
prevention
Use of high quality anti-virus
programs
Scan disks and files after using them
Scan all files you download from the
Internet
Scan word or excel
file email
attachments
before you read them
Use windows firewall programs
Update Virus Definition regularly
Use more secure operating systems like
Linux, Mac OS, etc.
Keep your computer's operating
system
patched with all critical updates.
Never open suspicious attachments
Regularly back up your files.
Don't open attachments with no
extension at all.
Symptoms
of infected computer
Unusual items appearing on the display,
including
graphics, odd messages, or
system
error messages.
Corrupted or inaccessible program files,
hard
disks, or diskettes.
Programs taking longer to start up,
running
more slowly than usual, or not
running
at all.
Unexplained decrease in the amount of
available system memory
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