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2. INTRODUCTION
Security Is the major issue in the computer field so, it
must be addressed by using some techniques in
order to secure our system.
Data can be hacked by the hackers and cause
damages to the computers. Some of the possible
damages that can be made to the computers are
malware virus, worms, spyware and cookies etc.

3. THREATS TO COMPUTER
SYSTEM
 MALWARE :-Malware' is an umbrella term used to refer to a variety of forms
of hostile or intrusive software, including computer viruses, worms, Trojan
horses, ransomware, spyware, adware, scareware, and other malicious
programs. It can take the form of executable code, scripts, active content,
and other software.
 VIRUS :-In addition to copying itself, a computer virus can also execute
instructions that cause harm. For this reason, computer viruses affect
security. They are part of malware. Very often, the term is also used for other
kinds of malware, such as Trojan horses and worms.
 WORMS :-A computer worm is a standalone malware computer program
that replicates itself in order to spread to other computers. Often, it uses a
computer network to spread itself, relying on security failures on the target
computer to access it. Unlike a computer virus, it does not need to attach
itself to an existing program.

4.  SPYWARE :-Spyware is a type of malware that is installed on a computer
without the knowledge of the owner in order to collect the owner's private
information. Spyware is often hidden from the user in order to gather
information about internet interaction, keystrokes (also known as
keylogging), passwords, and other valuable data.
 COOKIES :-A possible interaction between a web browser and a server
holding a web page in which the server sends a cookie to the browser and
the browser sends it back when requesting another page. Cookies are
arbitrary pieces of data, usually chosen by the web server, and stored on
the client computer by the browser.
 TROJAN :-In computers, a Trojan horse is a program in which malicious or
harmful code is contained inside apparently harmless programming or
data in such a way that it can get control and do its chosen form of
damage, such as ruining the file allocation table on your hard disk.

5. COMPUTER SECURITY
Computer security, also known as cybersecurity or IT security, is
the protection of information systems from theft or damage to
the hardware, the software, and to the information on them, as
well as from disruption or misdirection of the services they
provide.
 A computer should be used only by authorized users.
 Password should be changed regularly.
 Personal information and password should not be shared.
 Regularly update your antivirus software.

6.  DESKTOP SECURITY :- Using anti-virus software is one way to counter
computer threats. Moreover, these software are used after a virus has attacked
the computer. There are ways and measures by which we can restrict viruses to
enter into the computer. These measures collectively come under "Desktop
security" which includes software authorization, authentication, firewalls, encrypted
channels, anti-virus tools and user education.
 NETWORK SECURITY :-network security (or information security) is to provide
protection to the computer system from the hackers (intruders). Network
security focuses on protecting data resources from external attack and also from
simple mistakes made by the users within an organization.
 FIREWALL :- A firewall is a technique used in a secured computer system or
network to block unauthorized access and allow only the authorized user.
Firewalls can be implemented in either hardware or software, or a combination of
both.
 DIGITAL SIGNATURE :-In case of Cyber Crime, a digital signature plays a significant
role to ensure authenticity and thus protect security of a computer system. A
digital signature is a method for proving the authenticity of a message or
document or attachment or software sent through email.

7.  DIGITAL CERTIFICATE :- A digital certificate (also known as a public key
certificate or identity certificate) is an electronic document which uses a
digital signature to bind together a public key or password required
for decode and encoded document with an authentic identity such as the
name of a person or an organization, their phone numbers or address, and
so forth. The certificate can be used to verify that a public key belongs to
an authorized individual or organization.
 FILE ACCESS PERMISSION :-In a computer network or even in the
internet, some files or documents are made shareable and some are
made public. The protected sharable files and documents are shared
among few users or even by a group having the access rights. Access
rights are generally decided and given by the owner of the file or the
network administrator. Thus the three types of users can access a file or a
folder i.e. Owner, user having access rights, or all other users.

8. Software can be divided into different types depending upon their uses and
application. Software can be broadly divided into two categories such as
System Software & Application Software. Software required to run and
maintain basic components of computer system come under the
category of system software whereas software required to solve some
specific task of daily use is generally called application software. An
operating system is an example of system software while
documentation tool, a presentation tool, a spreadsheet tool are all examples
of application software. Even your favorite computer game is an example of
application software.
 System software
 Utility software
 Application software

9. Being an electronic device, a computer as such can not perform anything of
its own. The functions of all the physical components of a computer
system are guided by some instructions or program collectively known
as System Software. System Software controls all internal activities inside
a computer system and between all attached components of a computer
system. It controls all possible activities inside the computer system which can
be summarized as follows:
 Reads data and instructions through the input devices;
 Translates all data and instruction into computer understandable form and
vice versa;
 Controls all devices attached to the computer system;
 Processes and generates the result on the output devices;
Ex:- BIOS, Operating system, Device drives, Language processors.

10.  The basic input/output system (BIOS) is also
commonly known as the System BIOS. The BIOS is boot
firmware, a small program that controls various electronic
devices attached to the main computer system. It is
designed to be the first set of instructions run by a
Computer when powered on. The initial function of the
BIOS is to initialize system devices such as the RAM, hard
disk, CD/DVD drive, video display card, and other hardware.
The BIOS sets the machine hardware into a known state to
help the operating system to configure the hardware
components. This process is known as booting, or booting
up.

11.  Operating system provides a software
platform, on top of which, other programs,
called application programs are run. The
application programs must be written to run
on the environment of a particular operating
system. Our choice of operating system,
therefore, depends to a great extent on the
CPU and the other attached devices and the
applications we want to run. For PCs,
some of the most popular operating
systems are Microsoft Windows, Linux, Mac
OS, Solaris, BOSS, etc.

14.  As discussed above, a computer system understands only machine
language or binary language, also known as Low Level Language (LLL).
This language is extremely difficult to learn for a general programmer
and thus there is a need for some special language that is easy to learn
and understand for the programmer in order to interact with the
computer system. These special languages or set of commands are
collectively known as programming languages or High Level
languages (HLL). Some examples of High Level Programming
Languages are Basic, C, C++, JAVA, etc. These high level programming
languages can easily be translated into machine language and vice versa
using language translators like assembler or Interpreter or Compiler. These
translators are also known as language processors.

15.  Application software is a set of programs to carry out a specific task like
word processor, spreadsheet, presentation tools, library management
software, railway reservation, antivirus software, etc. Generally an
application software can perform only one specific job and can not be
used for something else. For instance, a library management software can
not be used for railway reservation system or a word processing
software is generally not used as a spreadsheet.
Application Software can be divided into different categories depending
upon their uses as follows:
 Utility Software
 General Purpose Application Software
 Specific Purpose Application Software
 Developer Tools