NCERT Solutions Class 12, Computer Science, Chapter- 12, Security Aspects
1. Why is a computer considered to be safe if it is not connected to a network or Internet?
Solution:
A computer is considered safe when not connected to a network or the Internet due to reduced exposure to external threats like malware and hacking attempts.
2. What is a computer virus ? Name some computer viruses that were popular in recent years.
Solution:
A computer virus is a piece of software code created to perform malicious activities and hamper resources of a computer system like CPU time, memory, personal files, or sensitive information. It infects other computer systems that it comes into contact with by copying or inserting its code into the computer programs or software (executable files).
Some computer viruses that were popular in recent years are CryptoLocker, ILOVEYOU, MyDoom, Sasser and Netsky, Slammer, Stuxnet, etc.
3. How is a computer worm different from a virus ?
Solution:
The major difference between a worm and a virus is that unlike a virus, a worm does not need a host program or software to insert its code into. Worms are standalone programs that are capable of working on its own. Also, a virus needs human triggering for replication (i.e. when a user opens/executes the infected file), while a worm replicates on its own and can spread to other computers through the network.
4. How is Ransomware used to extract money from users ?
Solution:
Ransomware is a type of malware that targets user data. It either blocks the user from accessing their own data or threatens to publish the personal data online and demands ransom payment in the form of Bitcoin cryptocurrency.
5. How did a Trojan get its name ?
Solution:
The name "Trojan" originates from the ancient Greek story of the Trojan Horse. Since the ancient Greeks could not infiltrate the city of Troy using traditional warfare methods, they gifted the king of Troy with a big wooden horse with hidden soldiers inside and eventually defeated him. Borrowing the concept, a Trojan is malware that looks like legitimate software, and once it tricks a user into installing it, it acts much like a virus or worm.
6. How does an adware generate revenue for its creator ?
Solution:
An adware is malware created to generate revenue for its developer. It displays online advertisements using pop-ups, web pages, or installation screens. Once adware infects a substantial number of computer systems, it generates revenue either by displaying advertisements or by using a "pay-per-click" mechanism to charge clients based on the number of clicks on their displayed ads.
7. Briefly explain two threats that may arise due to a keylogger installed on a computer.
Solution:
Two threats that may arise due to a keylogger installed on a computer are :
- Privacy Breach — Keyloggers can capture sensitive and personal information such as passwords, emails and private conversations. This information can then be accessed and misused by unauthorized individuals, leading to privacy breaches and potential identity theft.
- Data Leakage — Keyloggers have the capability to send the recorded keystrokes to external entities without the user's knowledge. This data leakage can result in confidential information falling into the wrong hands, compromising security and confidentiality.
8. How is a Virtual Keyboard safer than On Screen Keyboard ?
Solution:
Virtual Keyboard and On Screen Keyboard, both types of keyboards may look the same, but the difference is in terms of the layout or ordering of the keys. The on-screen keyboard of an operating system uses a fixed QWERTY key layout, which can be exploited by sophisticated keylogger software. However, an online virtual keyboard randomises the key layout every time it is used, thereby making it very difficult for a keylogger software to know or record the key(s) pressed by the user.
9. List and briefly explain different modes of malware distribution.
Solution:
The different modes of malware distribution are as follows :
- Downloaded from the Internet
- Spam Email
- Removable Storage Devices
- Network Propagation
- Downloaded from the Internet- Most of the time, malware is unintentionally downloaded into the hard drive of a computer by the user. Of course, the malware designers are smart enough to disguise their malware, but we should be very careful while downloading files from the Internet (especially those highlighted as free stuff).
- Spam Email- We often receive an unsolicited email with embedded hyperlinks or attachment files. These links or attached files can be malware.
- Removable Storage Devices- The replicating malware targets the removable storage media like pen drives, SSD cards, music players, mobile phones, etc. and infect them with malware that gets transferred to other systems that they are plugged into.
- Network Propagation- Some malware like Worms have the ability to propagate from one computer to another through a network connection.
10. List some common signs of malware infection.
Solution:
Common signs of some malware infection include the following:
- Frequent pop-up windows prompting us to visit some website and/or download some software.
- Changes to the default homepage of web browser.
- Mass emails being sent from our email account.
- Unusually slow computer with frequent crashes.
- Unknown programs startup as we turn on our computer.
- Programs opening and closing automatically.
- Sudden lack of storage space, random messages, sounds, or music start to appear.
- Programs or files appear or disappear without our knowledge.