CBSE Class 7 Computer Science Computer Virus Worksheet Set 01

Answer: A virus is a harmful program that attaches itself to another program or file and spreads when that program is run. A worm is a self-copying program that spreads on its own through networks without needing a host file.

Teacher's Note:
1. A virus needs a host and a user action.
2. A worm spreads by itself and can slow a network.

Answer: 1. Boot sector virus: infects the start-up area of a disk.
2. File infector virus: attaches to program files.
3. Macro virus: hides in documents that use macros.
4. Trojan horse: a harmful program disguised as a useful one.

Teacher's Note:
1. Each type targets a different part of the system.
2. Knowing the type helps in cleaning it.

Answer: A hacker is a person who explores computer systems in depth, and may do it with permission to improve security. A cracker breaks into systems without permission to steal or damage data.

Teacher's Note:
1. Both use technical skill, but the intention differs.
2. Illegal entry is a crime.

Answer: 1. Through infected pen drives or other storage devices.
2. Through email attachments and downloaded files.
3. Through unsafe websites and pirated software.
4. Over a network from an infected computer.

Teacher's Note:
1. Viruses move whenever infected files move.
2. Be careful with files from unknown sources.

Answer: 1. Install good antivirus software and keep it updated.
2. Scan pen drives before opening them.
3. Do not open unknown email attachments.
4. Avoid pirated software and keep backups.

Teacher's Note:
1. Prevention is better than repair.
2. Updates help the antivirus spot new viruses.

Answer: Examples: Quick Heal, Norton, McAfee, Kaspersky, Avast and Windows Defender (Microsoft Defender).

Teacher's Note:
1. Any three are enough.
2. Do not install two full antivirus tools together.

Answer: 1. Disconnect from the internet.
2. Update the antivirus and run a full scan.
3. Delete or quarantine the infected files as suggested.
4. Restart and scan again; restore data from a backup if needed.

Teacher's Note:
1. Quarantine keeps the file isolated.
2. A backup lets you recover lost files.

Answer: A Trojan horse is a harmful program that pretends to be a useful program or game. It does not copy itself like a virus, but it can steal data or give others control of the computer once the user runs it.

Teacher's Note:
1. The name comes from the wooden horse of Greek story.
2. It tricks the user into letting it in.

Answer: A firewall is a security system that monitors and controls data coming into and going out of a computer or network. It blocks unauthorised access and suspicious traffic.

Teacher's Note:
1. It acts like a gatekeeper for your network.
2. It works along with antivirus software.

Answer: A backup is a spare copy of data. If a virus damages or deletes files, you can restore them from the copy.

Teacher's Note:
1. Keep the backup on a separate device.
2. Then it is not affected if the main computer is infected.

Answer: harmful (malicious). It spreads when the host program runs.

Teacher's Note:
1. The key idea is that it damages or disturbs the system.
2. It cannot run alone.

Answer: triggered (activated). Such viruses are called logic or time bombs.

Teacher's Note:
1. They stay hidden until the set moment.
2. Then they perform the harmful action.

Answer: programmers, who write them with the intention to harm. They are not natural.

Teacher's Note:
1. Viruses are written by people.
2. They are not caused by a fault in the machine.

Answer: hackers and crackers. Crackers are the ones with harmful intent.

Teacher's Note:
1. Many ethical hackers work to make systems safer.
2. Do not call all hackers criminals.

Answer: program (application). Running it lets the virus load into memory.

Teacher's Note:
1. Just storing an infected file is not enough.
2. The virus needs the file to be run or opened.

Answer: False. A virus is software and affects programs and data, not hardware parts.

Teacher's Note:
1. It can make hardware misbehave but cannot break it physically.
2. Overheating or misuse breaks hardware.

Answer: False. They spread through storage devices, email and networks.

Teacher's Note:
1. Spreading is how a virus survives.
2. This is why shared files need scanning.

Answer: True. New viruses appear daily and updates add their signatures.

Teacher's Note:
1. An out-of-date antivirus misses new threats.
2. Turn on automatic updates.