Page 472 - Computer Science V2.0 Class 11

At the same time, they are also a threat to one’s security, as some of them may trick users. Spam may include offensive
material like profanity, pornography, or even viruses and other harmful software. Although it is possible to unsubscribe
from spam, the process is time-consuming. A software tool for blocking spam is frequently offered by email providers,
but it is not always efficient.
15.3.9 Denial of Service

A Denial of Service, or DOS attack renders a machine or network resource unavailable either temporarily or permanently
to its intended users. A DOS attack is typically carried out by sending a lot of false requests to the targeted machine
or resource, which eventually cause the system to become too busy to work. This prevents the processing of genuine
requests, resulting in a denial-of-service to them.

Match the following:
1. Phishing a. Replicates on network
2. Eavesdropping b. Pop-ups in browser for marketing
3. Worm c. An email from someone with pseudo identity
4. Trojan Horse d. Ethical and unethical
5. Hacking e. Secretly recording the conversation
6. Adware f. Looks useful but is harmful

15.4 Malware

Malware is a program that aims to hurt a computer, server, client, or computer network. Attackers use malware to
perform illegal actions on a user’s computer, such as data collection, network or system damage, data encryption for
ransom, and data erasure. Computer viruses, worms, Trojan horses, ransomware, spyware, and adware are examples
of malware. Installing anti-malware software and keeping it updated is necessary to protect the system from malware.

15.4.1 Viruses

A virus is a piece of software code that can damage your system by replacing or messing up the system files. Computer
viruses are like viruses that live in our bodies and copy themselves and damage cells. A typical virus attaches itself to
a program and can spread to another piece of code or file that has not been infected. So, the infection can spread
from one computer to another. Unsuspecting users may exchange files on discs, USB sticks, or over a network and
contribute to the spread of viruses (Fig 15.4).

Fig 15.4: Computer Virus
Computer viruses make several copies of themselves. They add their code to system programmes, files, or the boot
sector of hard drives, which makes them unusable. As a result, the system slows down or even stops functioning. The
viruses are mainly classified as boot sector, file infector, and macro viruses.

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