2. What is a computer virus?
• A computer virus is a computer
program that can copy itself and infect a
computer without permission or
knowledge of the user.
• A computer virus can only spread from
one computer to another when its host is
taken to the uninfected computer, for
instance by a user sending it over a
network or the Internet, or by carrying it
on a removable medium such as a floppy
disk, CD, or USB drive.
3. History of computer viruses
• 1981 Apple Viruses 1, 2, & 3
• 1980’s Fred Cohen
• 1987 Lehigh Virus
• 1988 The first anti virus software
• 1990 The first polymorphic viruses
• 1991 Symantec releases Norton Anti
Virus
• 1992 The Michelangelo Virus
• 1994 Kaos4 virus spreads via adult
websites.
4. Virus through the internet
• Today almost 87% of all viruses
are spread through the internet.
• Transmission time to a new host
is relatively low, on the order
of hours to days
• “Latent virus”
5. Symptoms of virus Attack
• Computer no longer boots up.
• Screen sometimes flicker.
• Computer runs slower then usual.
• PC speaker beeps periodically.
• System crashes for no reason.
• Files/directories sometimes
disappear.
• Denial of service (dos)….. & Many
More.
6. Examples of risky file types
• The following file types should be treated with
suspicion and be confirmed with the sender before
being opened:
– .exe
– .pif
– .bat
– .vbs
– .com
7. What to do when you find viruses
Firstly, you should call the administrator for
future action. In some cases it is not good to
start you computer from hard disk, because
the virus may active and then do some harm.
Make sure that you should get sure that it is
virus and what virus it is. It is important to
know what kind of virus we are dealing with.
Companies that make anti-virus programs
know what different viruses do and you can
go to their web pages and read about the
virus you have.
8. Cont……
When you start you computer you should do
it from a clean (non-infected) floppy diskette
and after that run the virus program. The
boot diskette should be write protected so
that virus can not infect the boot diskette too.
It is good to take a backup of the file that was
infected. Virus program could do some
damage to the file and that is why it is good
to have a backup.
It is good to let you, to know about the virus,
so viruses would not spread around so much.
9. How to protect from viruses
Best way to protect yourself is to prepare your computer
against viruses in advance. One way to protect you
computer is to use updated anti-virus program. When you
get an email attachment, you should first check the
attachment by checking the file with an anti-virus program.
One can protect the computer against boot sector viruses
by setting the BIOS to start from a hard disk rather than
from a floppy disk.
Write protection is a good way to prohibit against viruses.
Write protection works well in floppy disks, Windows NT
and UNIX, but not that well in Windows and Windows95.
10. What is a computer WORM ?
• A computer worm is a self-replicating
computer program. It uses a network to send
copies of itself to other nodes (computer
terminals on the network) and it may do so
without any user intervention.
• Unlike a virus, it does not need to attach itself
to an existing program. Worms almost always
cause harm to the network, if only by
consuming bandwidth, whereas viruses
almost always corrupt or modify files on a
targeted computer.
11. What are Trojan Horses ?
• A Trojan horse, also known as a trojan, is malware
that appears to perform a desirable function but in
fact performs undisclosed malicious functions.
Therefore, a computer worm or virus may be a Trojan
horse. The term is derived from the classical story of
the Trojan Horse.
• A program named "waterfalls.scr" serves as a simple
example of a trojan horse. The author claims it is a
free waterfall screen saver. When run, it instead
unloads hidden programs, commands, scripts, or any
number of commands without the user's knowledge
or consent.
12. Types of viruses
• Boot viruses
• Program viruses
• Multipartite viruses
• Stealth viruses
• Polymorphic viruses
13. How viruses get into
computers
• The four most common virus infections come from:
– File – A virus type that infects existing files on the computer
(approx. 40% of all viruses)
– Macro – A virus that runs as a macro in a host application
such as the MS Office applications (approx. 35%)
– VBScript – A virus that uses Windows VisualBasic Script
functionality (approx. 10%)
– Internet Worm – A virus that is primarily characterized by
it’s replication across the Internet (approx. 5%)
14. Basic virus defense
• Be cautious of files that you are not expecting and from
unknown senders.
• Many viruses automatically send files without the email account
owner’s knowledge. They can ‘piggyback’ on the email accounts
of senders you know.
• Be suspicious of messages that appear more than once in your
Inbox
• Be aware of sites offering free software downloads
15. Basic virus defense (cont.)
• Learn file extensions
– Your computer will display both an icon and a file
extension for every file.
– Open only file extensions you know are safe.
16. ANTIVIRUS
• Antivirus software are computer programs that
attempt to identify, neutralize or eliminate malicious
software. The term "antivirus" is used because the
earliest examples were designed exclusively to
combat computer viruses; however most modern
antivirus software is now designed to combat a wide
range of threats, including worms, phishing attacks,
Trojans, often described collectively as malware.
18. Removal Of Some Common Viruses
• You can remove some of the common
viruses without help of any antivirus
Program.
• Eg : New Folder.exe
• Autorun.inf ( from PDs etc)
19. New Folder.exe
• It looks just like an folder but actually it is a exe file.
• Step 1: Try deleting the file.
• It will delete if you haven’t executed it, if you’re unable to delete it
• Go to Task manager ( by pressing ctrl+shift+esc )
20. Go to Process Tab and
try finding that the
process for the exe file
and end the process.
Then Go to the same
folder containing the
exe file and delete it.
Then Open Search and
try finding the .exe files
of same size and delete
them all.
22. Cont…….
• The Command Prompt will Open Now. In Command prompt go to the drive
containing Autorun.inf
• Now Type In “ attrib –h –s –a” and press enter.
• This will remove drives attributes for all Hidden, System files.
• Now Type “ Delete autorun.inf” and press Enter.
• The Virus has been Successfully Removed.
23. Data Fellows F-Prot
EliaShim ViruSafe
ESaSS ThunderBYTE
IBM Antivirus
McAfee Scan
Microsoft Anti-Virus
Symantec Norton Antivirus
S&S Dr S&S Dr Solomon's AVTK.
Bit Defender 2008
24. * How computer viruses have spread
out around the world *
Computer viruses are a problem all over the world. The
following picture tells us how many times people have
accessed Data Fellows, a company that makes anti-virus
program F-Prot, more than 1,672,846 per month. It means that
people are interesting in virus information. One reason is that
people have to deal with viruses. Viruses in not only a problem
in Finland and USA, it is a problem around the world.
Today's most common virus is the macro virus. Cap virus is
one of the macro viruses. Last month there were 3100 Cap
macro virus accesses during the last 30 days in Data Fellows.
Next common virus was “Join” with 1171 accesses and third
common was Pen pal Greetings with 895 accesses.
27. conclusion
There are lots of viruses in the world and new viruses
are coming up every day. There are new anti-virus
programs and techniques developed too. It is good to
be aware of viruses and other malware and it is
cheaper to protect you environment from them rather
then being sorry. There might be a virus in your
computer if it starts acting differently. There is no
reason to panic if the computer virus is found.
It is good to be a little suspicious of malware when
you surf in the Internet and download files. Some files
that look interesting might hide a malware.
28. THE LAST WORD
“THE ONLY TRULY SECURE SYSTEM
IS ONE THAT IS POWERED OFF,
CAST IN A BLOCK OF CONCRETE, AND
SEALED IN A LEAD-LINED ROOM WITH
ARMED GUARDS AND EVEN THEN I
HAVE MY DOUBTS.”
