This document discusses viruses, antiviruses, and how to prevent virus attacks. It begins with definitions of viruses, malware, and spyware. It then covers virus languages, types of viruses like macro viruses, boot sector viruses, and worms. The document discusses symptoms of virus attacks and methods of prevention like using antivirus software and firewalls. It provides details on Windows Defender antivirus and how to enable secure logon, recognize dangerous file types, and determine when an email can be trusted. It concludes with information on removing shortcut viruses from files and drives.

1. Viruses and Antiviruses
By: Sarhad Baez

2. Introduction

3. Contents:
1. Introduction
2. Virus Languages
3. Virus Types
4. Symptoms of Virus Attack
5. Prevention from Computer Viruses
6. Windows Defender
7. Enable or disable secure logon
8. Recognizing dangerous file types
9. When to trust an e-mail message
10.Shortcut Virus
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4. Introduction
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What does malicious software(malware)
mean?
Software designed to deliberately harm your
computer. For example, viruses, worms, and
Trojan horses are malicious software. Also
known as malware.
What does Spyware mean?
Software that can display advertisements (such
as pop-up ads), collect information about you,
or change setting on your computer, generally
without appropriately obtaining your consent.
What is a virus?
A virus is a program that replicates itself. It spreads by making copies of itself on a
computer or by inserting computer code into program or operating system files.
Viruses don't always damage files or computers, but they usually affect a
computer's performance and stability. For a virus to infect a computer or to
spread, you usually have to do something, such as open an infected e-mail
attachment.

5. Virus Languages
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▪ ANSI COBOL(Common Business-Oriented Language)
▪ C/C++
▪ Pascal
▪ VBA (Visual Basic for Applications)
▪ Unix Shell Scripts
▪ JavaScript

7. ▪ Time Bomb Virus: is a virus program that works in
particular date to do special activity.
▪ Logical Bomb Virus: its destructive program that do an
activity when a certain action has occurred.
▪ Boot Sector Virus: its infects the boot sector, the virus is
loaded in to the main memory during system boots and
destroyed the data stored in the hard.
Virus Types
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8. ▪ Macros Virus: Its infects files that are created using
certain applications or programs that contain macros, like
word, excel, and power point.
• When opening the infected document the virus
loaded in to the main memory and destroyed the
data stored in the hard.
• These hide in documents that are shared via e-mail
or networks.
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Virus Types

9. ▪ Script Virus: programming languages that let the user create new
features and utilities it can be written by using java script or VBS
(Visual Basic Script) programs languages.
• The main sources of web scripting viruses are the web browsers
or infected web pages.
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Virus Types
▪ Worm Virus: Its computer code that spreads without user interaction, kind of
malicious code. It is blocking out the system so that its operations are slowed
down or stopped.
• Its self replicating information so fast that the entire network may
collapse.
• They do not infect files or damage them.

10. ▪ Trojan Horse is a malicious software program that hides inside other programs. It enters a
computer hidden inside a legitimate program, such as a screen saver. It then puts code into the
operating system, which enables a hacker to access the infected computer.
• Trojan horses do not usually spread by themselves; they are spread by viruses, worms, or
downloaded software.
• Its a kind of malicious code. it is usually disguises itself as a useful program or application if
executed the computer will be damaged.
• Do not reproduce by infecting other files.
• Its not self-replicate like worms.
• Its destructive program .
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Virus Types

11. Difference

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▪ Hackers:
▪ Professionals in information systems and
software.
▪ Helping, Inventing, and developing.
▪ White Hats.
▪ Crackers:
▪ Professionals in information systems and
software.
▪ Penetrating, Destroying, and Stealing.
▪ Black Hats.
What is the difference between Hackers
and Crackers?

13. ▪ Computer do not boots up.
▪ Files/directories sometimes disappear.
▪ The Command CTRL+ALT+DEL No Longer Works.
▪ Windows Shooting Alone when you use the internet
browsers.
▪ Performance Degradation.
▪ Screen sometimes flicker.
▪ PC speaker beeps periodically.
▪ System crashes for no reason.
▪ Denial of Service (DoS).
Symptoms of Virus Attack
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14. Prevention from Computer Viruses
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1. Installing an antivirus program and keeping it up-to-date can help defend your computer against
viruses. Like: Windows Defender.
2. Use your browser's privacy settings.
3. Use a pop-up blocker with your browser.
4. Do not open e-mail attachments. Many viruses are attached to e-mail messages and will spread as
soon as you open the e-mail attachment. It's best not to open any attachment unless it is
something you are expecting. Microsoft Outlook and Windows Mail help block potentially
dangerous attachments.

15. Prevention from Computer Viruses (Cont.)
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5. Do not run any download programs from the internet without scan it.
6. Back Up your programs and files periodically.
7. Turn on User Account Control (UAC) in your computer.
8. Use a firewall programs. Windows Firewall or any other firewall program can help alert you to
suspicious activity if a virus or worm attempts to connect to your computer. It can also block
viruses, worms, and hackers from attempting to download potentially harmful programs to your
computer.

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Windows Defender
Using Windows Defender
▪ Windows Defender is antispyware software that's included with
Windows and runs automatically when it's turned on.
▪ Using antispyware software can help protect your computer against
spyware and other potentially unwanted software.
▪ Windows Defender offers two ways to help keep spyware from
infecting your computer:
1. Real-time protection.
Windows Defender alerts
you when spyware
attempts to install itself or
to run on your computer. It
also alerts you when
programs attempt to
change important
Windows settings.

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2. Scanning options. You can use Windows Defender to scan for
spyware that might be installed on your computer, to schedule
scans on a regular basis, and to automatically remove anything
that's detected during a scan.
▪ When you use Windows Defender, it's important to have up-to-date
definitions.
Windows Defender
▪ Windows Defender uses
definitions to alert you to
potential risks if it
determines that software
detected is spyware or
other potentially
unwanted software.

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Enable or disable secure logon
Enable or disable secure logon (Ctrl+Alt+Delete)
It's important to keep your computer as secure as possible. One way to do
this is to enable secure logon, which requires you to press Ctrl+Alt+Delete to
log on.
When secure logon is enabled, another program (such as a virus or spyware)
can't intercept your user name and password as you enter it.
1. Click to open Advanced User Accounts. Administrator permission
required If you are prompted for an administrator password or
confirmation, type the password or provide confirmation.
2. Click the Advanced tab, select the Require users to press
Ctrl+Alt+Delete check box, and then click OK.

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Recognizing dangerous file types
Dangerous file types are those that have the potential to contain viruses
or spyware that might damage your information or the programs on
your computer.
➢ The types of files that are considered dangerous are usually program
files (.exe), macros, or .com files. The vast majority of files with these
extensions do not contain viruses. However, when you download or
receive these types of files in e-mail, you should not open them
unless you trust the source or you were expecting the file.

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Recognizing dangerous file types
Most common file name extensions
The following table describes file name extensions that might indicate
that a file is dangerous.
Extension Type of file
.exe Program
.com MS-DOS program
.pif Shortcut to MS-DOS program
.bat Batch file
.scr Screen saver file

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Recognizing dangerous file types
Notes
➢ Some viruses use files with two extensions to make dangerous files
look like safe files.
▪ For example, Document.txt.exe or Photos.jpg.exe. The extension
farthest to the right is the one that Windows will try to open. It
is extremely rare that a legitimate file would have two
extensions, so avoid downloading or opening this type of file.
➢ There are files that are safer to download than program or macro
files, such as text (.txt), or image (.jpg, .gif, .png) files. However, you
should still be wary of unknown sources, as some of these files have
been known to have specially crafted formats that can exploit
vulnerabilities in computer systems.

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When to trust an e-mail message
Here are some questions you can ask yourself to help decide
whether to open an e-mail message or attachment.
1. Do you know the person who sent you the e-mail message?
▪ Is the message from a person or organization that you know and trust?
If the message is from someone you've never heard of, be cautious. If
it appears to be from someone you know, be suspicious or
inappropriate subject lines such as RE: Your archive, or attachments
that contain program files (executable files) such as price.exe. Many
viruses can mimic e-mail addresses to make it look like the message is
from someone you know.
2. Have you received e-mail from the sender before?
▪ If you know the person or company sending the message, but you've
never received e-mail from them before, make sure you know why
you're getting a message now. Check the text in the Subject line and
the file name of the attachment, if there is one. If any of that text
seems suspicious, delete the message or make sure it is scanned using
up-to-date antivirus software before opening it.

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When to trust an e-mail message
3. Were you expecting e-mail from this sender?
▪ Were you expecting a message or attachment from the sender with
the subject or file name? If not, send a separate e-mail message to the
sender (don't click Reply) and ask if he or she really sent this e-mail
message.
4. Does the subject line or attachment file name make sense?
▪ Junk e-mail and viruses often use random characters or words in the
subject line or attachment file name to bypass content or spam filters.
An unexpected message from a friend that has gibberish in the subject
line might be sent by a virus that mimics (or spoofs) your friend's
e-mail address. Subject line messages that urge you to do something,
for example, "Important! Open the attachment immediately!" might
indicate that the e-mail message might not be safe to open. An
attachment with a double file name extension, such as Sample.jpg.exe,
is not a file that someone would normally send, and could be a virus.

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When to trust an e-mail message
What is a digital signature?
A digital signature is an electronic security mark that can be added to files. It
allows you to verify the publisher of a file and helps verify that the file has
not changed since it was digitally signed.
If the file doesn't have a valid digital signature, there's no way for you to be
sure that the file is actually from the source it claims to be from, or that it
has not been tampered with (possibly by a virus) since it was published. It's
safer to avoid opening the file unless you know for certain who created it
and whether the contents are safe to open.
Even a valid digital signature doesn't verify that the contents of the file are
harmless. You must decide if you should trust the contents of the file based
on the identity of the publisher and where you are downloading the file
from.

26. Shortcut Virus

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Shortcut Virus
Shortcut Viruses: A shortcut virus make your all data in a
shortcut icon as like a folder or other. An image can be
shortcut or a media file as like audio, video or any document
file also can be show as a shortcut icon.
➢ Most shortcut virus ends with .EXE, .VBS,.LNK and .INI file
extensions.

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Remove Shortcut Virus
➢ The steps to remove shortcut virus from your usb in your computer.
✓ Open "Run" click on "Start Menu" >>>Run >>> type "cmd" and
click OK.
✓ Now you will see the cmd (command prompt) has been opened,
if your usb external drive name is h: then command is like bellow
code,

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Remove Shortcut Virus
attrib –h –r –s /s /d H:*.*
Note:
here H: is your system drive letter which is
affected with shortcut virus.
➢ Attrib is a MS- DOS command which help us to alter the
properties of the file/ folder.
➢ -h stands for ‘’ remove hidden“
➢ -r stands for ‘’ remove read only “
➢ -s ‘’ unmark system ‘’.

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Shortcut Virus Removal With BAT File [Batch File]
1. Open Notepad from your computer/laptop.
2. Type or copy the below code as it is on notepad.
3. Make sure to replace Drive with your drive name. Ex: H:
4. Now click on Save As… by clicking on File tab in notepad and change
the save as type to “All files(*.*)” from “Text documents” and rename it
to removeshortcutvirus.bat and save it on your desktop.
5. Now close notepad and go to desktop and double click on the BAT file
that you have just created.
6. All shortcut viruses from the respective drive will now be removed in
couple of seconds and your original files will be back. Enjoy.
@echo off
attrib -h -s -r -a /s /d Drive:*.*
attrib -h -s -r -a /s /d Drive:*.*
attrib -h -s -r -a /s /d Drive:*.*
@echo complete