This document discusses various aspects of computer security, including physical security, software security, and data security. It outlines threats like theft, fires, viruses, and disk failure. It recommends measures like locks, alarms, badges, backups, antivirus software, passwords, encryption, and transaction logs to protect hardware, software, data and ensure data integrity. Regular backups stored securely offsite are emphasized to prevent data loss from hardware or software issues.

1. 1
System Security
Chapter no 16

2. 2
Computer Security
 Computer security is concerned with taking care
of hardware, Software and data
 The cost of creating data again from scratch can
hardware or program lost.
 Loss of data can have various consequences
 Bad business decision
 Loss of goodwill from customers
 Cash flow problems
 Adverse publicity from the press
 Late delivery of goods
 Failure to receive payment

3. 3
Physical security
 Computer equipment and its data need
to be protected from physical harm
 These include natural ones such as
 Fire
 Lighting
 Water damage
 Theft

4. 4
Computer theft
 There are many ways of making sure
that unauthorized people are denied
access to a system through use of
keyboard locks and password
 It is more difficult to prevent a thief from
picking up a system and stealing it
 Locks alarmed on circuit board and tags
are method of hardware protection

5. 5
Preventing theft
 Note the serial no of computers and
peripherals
 Lock the computers in case and key
should be safely saved
 Data should be backed up regularly
 All staff aware of security
 All staff wear security badge which
contains their photograph, name

6. 6
Protection from fires
 Fireproof doors help contain fire
 Use Smoke detectors
 Use gas folding systems are used in
large computer installations

7. 7
Protection from dust and
extremes of temperature
 Air conditioning is more important for
larger mainframe system where the
temperature and humidity must be
controlled
 The air must also be pure and filtered in
this way

8. 8
Software Security
 Viruses
 Viruses are programs the purpose of which is
to disrupt the sensible use of computer.
 Many viruses do little more than display
message on the screen
 Some are designed to act after a certain
period of time which drop off the screen or
erased the entire content of hard disk
 Viruses are able to spread from one disk to
other

9. 9
Anti virus software
 Antivirus software can be used to scan
the computer’s memory and disks to
detect the viruses
 Any viruses detected are then removed
using the software

10. 10
Avoiding viruses
 Don’t buy secondhand software
 Check your computer for viruses if it has
been recently repaired
 Be suspicious of all software which are
freeware ,shareware
 Not to use too many computers
 Install antivirus software which check the
hard disk every time the system is booted up

11. 11
Backing up data
 Means taking the copy of the data and
keeping it away from the computer in a
secure place.
 It is not good keeping a back up copy on the
same disk
 The most common way to lose a file is
through user error by deleting the file
 There are software packages available to
recover such data

12. 12
Rules of backing up
 Never keep backup disks near the computer
 One set of back up disks in a different place
 If data is expensive to recreate then invest in
a fire-proof safe to protect your backups
against theft and fire
 Placing important computer files in safe place
so that they can be found easily if needed
,which is called archiving

13. 13
Disk failure
 All micro computers will suffer at least one serious fault during
their lifetimes
 A typical hard disk failures mean time is between 20000 to
200000 hours
 This mean if computer was used for 12 hr per day then it means
that hard disk will break down one about six years
 If a computer was used for network server then used 24 hr so its
mean break down will every 27 months
Avoiding disk failure
 Back up copies of programs and data on a hard disk should be
taken at regular interval for this tape streamers is used
 Floppy disk is also used for backup disk data
 Use two hard disks in parallel with each other

14. 14
Protecting files
 Password is keyed in which is never shown in
screen
 Use software to limit each user’s access to
only those files that are needed for the
performance of their particular job
 To restrict access to a computer’s OS for
inexperienced users
 Restricted access can also be used to
prevent people from copying data from the
hard disk to a floppy disk

15. 15
Encryption
 Files contain sensitive data are encrypted or coded
 If a tape or disk containing sensitive files is stolen it
would then be impossible to read the data without
decoder
 Encryption is also used when important data is
transmitted from one place to other
 The data is coded before being sent and then
decoded at the other end.
 Both processes are performed automatically by
computers
 When people are making payments for goods bought
over internet using a credit or debit card the details
are always encrypted

16. 16
Data integrity
 Is concerned with the correctness of the data
Errors may be introduced into data in a variety
of ways They can be introduced when the
person typing in the data misreads it off a
source document or if machine errors corrupt
the data Validation and verifications checks
are performed on data to ensure its integrity

17. 17
Data Security
 Is concerned with keeping the data safe
from the various hazards that could
destroy it.

18. 18
Transaction Logs
 When you make changes to the data in a file
you usually delete the old information and
replace it with the new information
 If you have a bank or building society
account, money added to your account or
taken out needs to be recorded
 Each bit of business is called transaction
 The account statement showing the amounts
entering and leaving the account shows