INTRODUCTION TO COMPUTER

VIRUSBY YouQTM

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What is MALWARE ? Viruses, worms, Trojans, and bots are all part of a

class of software called malware. Malware or malicious code is short for malicious

software. It is code or software that is specifically designed to damage, disrupt, steal, or in general inflict some other “bad” or illegitimate action on data, hosts, or networks.

Malware cannot damage the physical hardware of systems and network equipment, but it can damage the data and software residing on the equipment.

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Virus A computer virus is a software program with a

ability to make copies of itself ,which attacks itself to other applications or files.

A virus cannot run by itself; it requires that its host program be run to make the virus active.

 Almost all viruses are attached to an executable file .

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The Computer Viruses are generally classified as follows

1) Boot virus2) TSR (Terminate and stay resident) 3) File infecting viruses (Program virus)

4) Micro virus5) Multipartite

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Boot viruses Boot viruses infects the boot records of hard

disk and floppy disks. Generally these are considered more dangerous than program viruses.

A boot record infector is a piece of malware that inserts malicious code into the boot sector of a disk.

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TSR (Terminate and stay resident) A TSRS virus is a virus that stays active in

memory after the application (or bootstrapping, or disk mounting) has terminated.TSR viruses can be boot sector infectors or executable infectors. The Brain virus is a TSR virus.

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FIV(Program viruses) These viruses infect program files, which have

extensions such as .COM,.EXE.,SYS.,DLL,.OVL, or .SCR. program files are attractive targets for computer virus because they are widely used and have relativity, simple formats to which viruses can attach themselves.

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Macro virus These viruses infects data files. For example,

Microsoft word document and template files are susceptible to macro virus attacks they spread rapidly as infected documents are shared on networks or downloaded from internet sites.

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Multipartite A multipartite virus is a virus that can infect

either boot sectors or executables. Such a virus typically has two parts, one for each type. When it infects an executable, it acts 3 as an executable infector. When it infects a boot sector, it works as a boot sector infector.

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Types of Viruses Worms Trojan Horse Bombs

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Computer Worm A computer worm is a standalone

malware computer program that replicates itself in order to spread to other computers.

Examples: Klez, Nimda, Code Red etc.

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Trojan horse Viruses Trojan horse, or Trojan, is any

malicious computer program which is used to hack into a computer by misleading users of its true intent.

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Logic bombs logic bombs that execute a certain payload

at a pre-defined time or when some other condition is met. This technique can be used by a virus or worm to gain momentum and spread before being noticed.

Logic bombs are usually timed to do maximum damage.

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How do viruses work? Once a virus gains access to a computer, its effects can vary.

Possible attacks include • Replicating itself • Interrupting system/network use • Modifying configuration settings • Flashing BIOS • Format hard drive/destroy data • Using computer/network resources • Distribution of confidential info • Denial of Service attacks

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Sources of Computer Virus Attack Removable media or drives • Downloading Internet files • E-mail attachments • Unpatched software and services • Poor Administrator passwords • Poor shared passwords

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Computer Security

Patching the operating system• Patching services • Patching client software • Passwords • Antivirus software • Firewalls

Virus prevention

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Perform Basic Computer Safety Maintenance

Use an Internet Firewall Update Your Computer Virus Detection (Antivirus software) Strong Passwords Valid Certificates before installing Software