What is Security, Virus, and types of Viruses?

Q1. What is Security? Discuss its different approaches or How the security maintained on a computer? 

SECURITY:

• It is a system of safeguards designed to protect a computer system and data from intentional and accidental damage or access by unauthorized persons.
• A computer system must be protected from unauthorized persons. Different methods have been planned to give access to authorized persons. For this purpose there are four approaches.
• What you have: You may have a key, token, or a card to give you physical access to the server room or computer building.
• What you know:  IDs and Passwords are given to users to access the computers.
• What you do:  Authorized users put their signatures on the documents to confirm their authority.
• What you are: Some security measures are biometrics-biological means of identification e.g. fingerprints, voice recognition, eye retina etc.

Q2. What is a Virus? What are the causes of Virus? 

VIRUS:

• A virus is a program that disturbs the normal execution of the programs.
• A virus is a program that attaches itself with other executable files by modifying them so that the virus program is also loaded and executed with the execution of these programs.
• Virus is a destructive program containing code that can generate copies of it and attaches itself with other programs so that it is automatically executed when those programs are executed.
• A virus is a program designed by a computer programmer to do a certain unwanted function.
• The virus program can be simply annoying like displaying a happy face on the user's screen at a certain time and date.
• A virus usually performs destructive operations by deleting or modifying the data on storage devices attached to the computer.
• Virus cannot physically destroy the hardware.
• Some virus may make invisible changes in the user’s data.
• A virus may make network resources unavailable to the users.
• A virus may detect some special information e.g. password, pin code etc. and transfers it to other users on the network.
• Virus infects computers data and can costs a lot of time and money to correct it.

CAUSES OF VIRUSES: 

• Emails, Networks, Removable Storage media, Pirated software are ways through which a virus reaches from one computer to another.

Emails:

 • Computers are infected due to receiving of emails containing virus programs.
• When a user opens an infected email, the virus is also loaded into the memory and attaches itself with other programs.
• You cannot get a virus from a plain email message. Modern email programs provide the ability to allow users to format email messages with HTML and attach scripts to them for various purposes and it is possible for a hacker to attempt to spread a virus by building a virus script into an HTML type of email message. 

Networks: 

• Virus is also spreading by using Internet and other networks
• When you are accepting software or scripts on Internet sites or reading mail from unknown senders it is wrong to run a program from that site or sender without checking it with an anti-virus program.
• When you download a file from the internet or from a shared disk on the network, the infected files may be attached with the downloaded data that ultimately infects the computer.

Removable Storage Media: 

• You can transfers the data from one computer to another through some removable media like floppy disks, CDs, or flash drives; therefore, when you copy the data using removable storage, the infected files can be transferred to your computer.

Pirated software: 

• The virus can also infect your computer by the use of pirated software (The software without license is called pirated software).
• Some companies may intentionally attach some virus programs into their software. This program will only activate when it does not find licensed files on the computer.

Q3. What are the different types of Virus? 

TYPES OF VIRUSES: 

• Boot Sector Virus, Chernobal virus, Logic Bomb, Trojan Horse, RedLof etc.

 Boot Sector Virus:

• Boot sector virus modifies the boot sector (the first sector which contains the instructions to automatically load OS in memory) program and is loaded in the computer memory whenever the computer is turned on.
• This virus is attached with system executable files i.e. .exe, .com and .dll files.
• When the user uses these files, the virus performs destructive operations and destroys all the data files.

Chernobal virus: 

• It deletes all the Microsoft office files.
• It also deletes the partition information from the disk.
• User cannot access files from the disk because of this virus.

Logic Bomb: 

• It is a virus that is activated on the basis of a logical condition.
• The virus instruction is executed if the logical condition is true.
• It is activated on a certain date and time.
• The bomb can be discovered by chance.

 Trojan horse: 

• It is a part of some computer programs e.g. destructive instructions inside the game programs.
• When the infected program (game) runs on the system, then this virus is activated.
• An example of Trojan horse is FORMAT C instruction which is executed with the execution of a game.

RedLof: 

• It is polymorphic virus written in VB Script.
• It infects the Folder.htt file which is the part of Windows Active desktop.
• It appends itself to other infected files on the hard disk and causes destruction. Some viruses make unnoticeable changes. They corrupt data being used. Some viruses may make data unusable. A virus may detect some special information like passwords or sensitive data. It may send the data to some other user on a network. For example a virus may read the pin code or credit card number and then send it to another user. A virus may also make some resources unavailable to the users. For example, a virus may start sending data on a network. The network may become unavailable for the users.