How to Prevent Computer Security Threats

THREAT TO SECURITY: 

A threat is defined as a computer program, a person, an accident, or events that violate (or break) the security system. A threat causes loss of data and attacks data privacy. The realization or understanding of a threat is known as an attack. 

Threats may be categorized by the type of activity or by the type of the attacker. Three are four general categories of attacks:

Interruption:

This type of attack does not allow authorized users to access the system. This type of attack is also known as a denial of service attack. In this type of attack, some components of a system are destroyed or become unavailable. For example, a hard disk may be destroyed, or a communication line is cut off, etc.

Interception:

In this type of attack, unauthorized persons or programs can access computer resources (such as important information stored on I computer) The attacker can illegally copy some important data programs. The data can also be modified. Modified data can be recovered from backup, but the confidential information is leaked out.

Modification:

In this type of attack, unauthorized users can delete or modify the important information stored in a computer system.

Fabrication:

In this type of attack, an unauthorized party insets counterfeit information (i.e false information) into the system. For example, the addition of records into a database file or adding an amount into a bank account of an online system.

PROGRAM THREATS:

Mostly the attackers use computer programs to break the security system of a computer and to access the computer resources. The computer programs that are used to access computer resources illegally or to damage them are known as medication programs or malware. These programs spread themselves to other computers via-e-mail or infected flobby disks (or CDs) etc. Malicious programs can be classified as follows:

Trap Door:

A trap door is a secret point in a program that bypasses normal security access procedures and thus the unauthorized person may get access to the system. It means that the trap door is a part of any program, which is used to bypass the protection mechanism. 

For example:

In a UNIX system, a trap door allows an attacker to easily enter the system by giving the login name of ''door'' (i.e root spelled backward) as a superuser without supplying a password.

Login Bomb:

A login bomb is a code segment embedded in some programs that cause the program to ''explode'' when certain conditions are met. Examples of conditions that can be used as triggers for a logic bomb are the presence or absence of certain files, a computer may be deleted or corrupted.

For example:

 This type of virus may be created and installed by a programmer who is working in an organization temporarily. The logic bomb is installed in an accounting program to check for his/her name in the organization's payroll system. If the employee (programmer) is terminated, the logic bomb is triggered and the program may delete files payroll system or it may some other destructive actions. 

Trojan Horse:

A code segment that is a part of some program, which is used to perform destructive functions, is called Trojan Horse. It can be used as a security breaking program. 

For example:

To gain access to the files of any type of user on a shared system, a user may create a Trojan Horse program that when executed in a system, modifies the invoking user's file permission so that the files are readable by any user in a system.

In some cases, Trojan Horse performs some unwanted or harmful functions, but in other cases, it performs useful functions for its creator.

 For example:

when it executes, it deleted all the user's files. It may also display the current date, or it may display messages for advertising of a particular product. It may also make duplicate copies of all the user's files.

Bacteria:

Bacteria is a program that repeatedly replicates itself. It does not perform any destructive function, but it consumes a large amount of storage area on the disk. Thus the speed of the system slows down.

Virus:

A virus is a malicious program that attaches itself to other executing program files by modifying these files. It is self-replicating and is designed to infect other programs. It is a segment of code embedded in a legitimate program...

A program that is infected by a virus is known as an infected program. When an infected program is loaded for execution, the virus is automatically loaded into the main memory and attaches to all those programs that are in the memory or loaded into the memory.

Causes of Virus:

The following are the means through which viruses may be transferred from one computer to another computer.

• E-mail
• Networks
• Removable Storage Media
• Pirated Software

E-mail:

Nowadays, most of the viruses spread through receiving e-mail messages that contain viruses. When a user opens such an infected message, the virus is also loaded into the computer memory and attaches copies of itself with many other files loaded in the memory. This virus is also transferred to other computers when e-mail messages are sent from the infected computer to these computers.

Networks:

Another way of spreading a virus is through the Internet and other networks.

For example:

when we download some executable files or any type of data 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:

One important means of exchanging data is through the use of removable media like floppy disks, CDs, and flash devices. So. when we copy the data from one computer to another by using removable media, the infected files can be transferred to our computer.

 Pirated Software:

Virus programs can also infect our computer system through pirated software. The software, which is installed in our computer system without a license is known as pirated software.  This program will only activate when it does not find some special files like license files on the computer system.

Worm:

The worm is a program, which spreads itself throughout a network. It uses a network connection to spread from a computer connected to the network. It usually, shutdowns the entire network. It is also replicated in the host machine. This program can also be used to break the user password.