By MARUF HASAN

Definition

EncryptionIn cryptography, encryption is the

process of transforming information

(referred to as plaintext) using an

algorithm (called cipher) to make it

unreadable to anyone except those

possessing special knowledge,

usually referred to as a key. The

result of the process is encrypted

information (in cryptography,

referred to as cipher text).

Encryption has long been used by

militaries and governments to

facilitate secret communication.

Encryption is now commonly used

in protecting information within

many kinds of civilian systems.

VIRUS A computer virus is a

computer program that can copy itself and infect a computer. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.

A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

A computer worm is a self-replicating malware computer program. It uses a computer network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.

VIRUS (contd.)

A Trojan horse, or Trojan,

is malware that appears to

perform a desirable

function for the user prior

to run or install but instead

facilitates unauthorized

access of the user's

computer system. "It is a

harmful piece of software

that looks legitimate.

Users are typically tricked

into loading and executing

it on their systems". Trojan

horses may allow a hacker

remote access to a target

computer system.

Spyware is a type of malware that

can be installed on computers, and

which collects small pieces of

information about users without their

knowledge. The presence of

spyware is typically hidden from the

user, and can be difficult to detect.

Spyware programs can collect

various types of personal

information, such as Internet surfing

habits and sites that have been

visited, but can also interfere with

user control of the computer in other

ways, such as installing additional

software and redirecting Web

browser activity. Spyware is known

to change computer settings,

resulting in slow connection speeds,

different home pages, and/or loss of

Internet connection or functionality

of other programs.

VIRUS (contd.)

Spam is the use of

electronic messaging

systems (including most

broadcast media, digital

delivery systems) to

send unsolicited bulk

messages

indiscriminately. While

the most widely

recognized form of

spam is e-mail spam.

Phishing is the

criminally fraudulent

process of attempting to

acquire sensitive

information such as

usernames, passwords

and credit card details

by masquerading as a

trustworthy entity in an

electronic

communication.