1. Computer Security Risks
What is a computer security risk?
p. 556 - 558 Fig. 11-1 Next
Event or action that causes loss of or damage to
computer system
2. Virus
A computer virus is a computer program that can replicate
itself and spread from one computer to another. The term
"virus" is also commonly but misused to refer to other types
of malware, including but not limited to adware and
spyware programs that do not have the reproductive ability.
A true virus can spread from one computer to another (in
some form of executable code) when its host is taken to the
target computer; for instance because a user sent it over a
network or the Internet, or carried it on a removable
medium such as a floppy disk, CD, DVD, or USB drive.
3. Types of Virus
Not all computer viruses behave, replicate,
or infect the same way. There are several
different categories of viruses and malware.
Below I list and discuss some of the most
common types of computer viruses.
4. Trojan Horse
Trojan Horse:
A Trojan horse program has the appearance of having a useful and desired
function. While it may advertise its activity after launching, this information
is not apparent to the user beforehand. Secretly the program performs other,
undesired functions. A Trojan Horse neither replicates nor copies itself, but
causes damage or compromises the security of the computer. A Trojan
Horse must be sent by someone or carried by another program and may
arrive in the form of a joke program or software of some sort. The malicious
functionality of a Trojan Horse may be anything undesirable for a computer
user, including data destruction or compromising a system by providing a
means for another computer to gain access, thus bypassing normal access
controls.
5. Worms
Worms:
A worm is a program that makes and facilitates the distribution
of copies of itself; for example, from one disk drive to another,
or by copying itself using email or another transport
mechanism. The worm may do damage and compromise the
security of the computer. It may arrive via exploitation of a
system vulnerability or by clicking on an infected e-mail.
6. Types of virus continued ……
Bootsector Virus:
A virus which attaches itself to the first part of the hard disk that is read by
the computer upon bootup. These are normally spread by floppy disks.
Macro Virus:
Macro viruses are viruses that use another application's macro
programming language to distribute themselves. They infect documents
such as MS Word or MS Excel and are typically spread to other similar
documents.
Memory Resident Viruses:
Memory Resident Viruses reside in a computers volitale memory (RAM).
They are initiated from a virus which runs on the computer and they stay in
memory after it's initiating program closes.
7. Types of virus continued ……
Root kit Virus:
A root kit virus is an undetectable virus which attempts to allow someone to
gain control of a computer system. The term root kit comes from the Linux
administrator root user. These viruses are usually installed by Trojans and are
normally disguised as operating system files.
Polymorphic Viruses:
A polymorphic virus not only replicates itself by creating multiple files of itself,
but it also changes it's digital signature every time it replicates. This makes it
difficult or less sophisticated antivirus software to detect.
Logic Bombs/Time Bombs:
These are viruses which are programmed to initiate at a specific date or when a
specific event occurs. Some examples are a virus which deletes your photos on
Halloween, or a virus which deletes a database table if a certain employee gets
fired.
8. Stand-Alone Utility Programs
What is a virus?
p. 425 - 426 Fig. 8-36
Potentially damaging computer program
Affects computer without user’s knowledge
SIGNS OFSIGNS OF
VIRUSVIRUS
INFECTIONINFECTION
• An unusual message or image is displayed on the
computer screen
• An unusual sound or music plays randomly
• The available memory is less than what should be
available
• A program or file suddenly is missing
• An unknown program or file mysteriously appears
• The size of a file changes without explanation
• A file becomes corrupted
• A program or file does not work properly
• System properties change
•The operating system runs much slower than usual
9. Stand-Alone Utility Programs
What is an antivirus program?
p. 426 Fig. 8-37
Identifies and removes viruses in memory, storage
media, and incoming files
Must be updated frequently
10. Internet and Network Attacks
What is an antivirus program?
p. 560 - 561 Fig. 11-4 Next
Identifies and removes
computer viruses
Most also protect against
worms and Trojan
horses
11. Internet and Network Attacks
What are viruses, worms, and Trojan horses?
p. 558 Next
VirusVirus is a
potentially
damaging
computer
program
WormWorm copies
itself repeatedly,
using up
resources
and possibly
shutting down
computer or
network
Trojan horseTrojan horse
hides within
or looks like
legitimate
program until
triggered
Payload
(destructive
event) that is
delivered when
you open file, run
infected program,
or boot computer
with infected disk
in disk driveCan spread
and
damage
files
Does not
replicate
itself on
other
computers
12. Internet and Network Attacks
How can a virus spread through an e-mail message?
p. 559 Fig. 11-2 Next
Step 1. Unscrupulous
programmers create a
virus program. They hide
the virus in a Word
document and attach the
Word document to an e-
mail message.
Step 2. They use
the Internet to
send the e-mail
message to
thousands of users
around the world.
Step 3b. Other users do not
recognize the name of the
sender of the e-mail message.
These users do not open the
e-mail message. Instead they
delete the e-mail message.
These users’ computers are
not infected with the virus.
Step 3a. Some
users open the
attachment and
their computers
become infected
with the virus.
13. Internet and Network Attacks
How can you protect your system from a macro virus?
p. 560 Fig. 11-3 Next
Set macro security level in applications that allow you to write
macros
Set security level so that
warning displays that
document contains macro
Macros are instructions
saved in an application,
such as word processing
or spreadsheet program
14. Keeps file
in separate
area of hard disk
Internet and Network Attacks
How does an antivirus program inoculate a program
file?
p. 561 Next
RecordsRecords
informationinformation
about program suchabout program such
as file size andas file size and
creationcreation
datedate
AttemptsAttempts
to removeto remove
any detectedany detected
virusvirus
UsesUses
informationinformation
to detect ifto detect if
virus tampersvirus tampers
with filewith file
QuarantinesQuarantines
infectedinfected
files that itfiles that it
cannotcannot
removeremove
15. Internet and Network Attacks
What is a firewall?
p. 563 Fig. 11-7 Next
Security system consisting of hardware and/or
software that prevents unauthorized intrusion
16. Unauthorized Access and Use
What are other ways to protect your personal computer?
p. 565 Fig. 11-9 Next
Disable file and printer sharing on
Internet connection
17. User Authentication(login)
What is a user name?
p. 566 Fig. 11-10 Next
Unique combination of characters that identifies user
Password is private
combination of
characters associated
with the user name
that allows access
to computer
resources
18. Tips for security
What are some tips for preventing virus, worm, and
Trojan horse infections?
p. 562 Next
Install a personal
firewall program
If the antivirus
program flags an
e-mail attachment
as infected, delete
the attachment
immediately
Never start a
computer with
removable media
inserted
Never open an
e-mail attachment
unless you are
expecting it and
it is from a
trusted source
Install an antivirus
program on all of
your computers
Check all
downloaded
programs for
viruses, worms,
or Trojan horses
19. Software Theft
What is a license agreement?
p. 570 Fig. 11-15 Next
Right to use software
Single-user license agreement allows user to install software
on one computer, make backup copy, and sell software
after removing from computer
20. Backing Up — The Ultimate
Safeguard
What is a backup?
p. 576 Next
Duplicate of file, program, or disk
Full backupFull backup
all files in
computer
Full backupFull backup
all files in
computer
Selective backupSelective backup
select which files
to back up
Selective backupSelective backup
select which files
to back up
Three-generationThree-generation
backupbackup
preserves
three copies of
important files
Three-generationThree-generation
backupbackup
preserves
three copies of
important files
In case of system failure or corrupted files,
restorerestore files by copying to original location
21. Information Privacy
What are spyware, adware, and spam?
p. 583 - 584 Fig. 11-29 Next
Spyware is program
placed on computer
without user’s
knowledge
Adware is a program
that displays online
advertisements
Spam is bogus
e-mail message sent
to many recipients
22. Information Privacy
How can you control spam?
p. 584 Next
Collects spam in
central location
that you can
view any time
Service that
blocks e-mail
messages from
designated
sources
E-mail filteringE-mail filtering
Sometimes
removes valid
e-mail messages
Attempts to
remove spam
Anti-spam programAnti-spam program
