Virus Detection (Anti-Virus) – JSS3 Computer Studies Lesson Note (Third Term)

An antivirus is a program that detects, prevents and removes computer viruses and other malicious software from a computer.

Behavioural objectives

By the end of the lesson, students should be able to:

1. explain what an antivirus is and state its main function;
2. define malware and a computer virus;
3. describe common types of malware and the signs of infection;
4. explain how an antivirus detects and removes threats;
5. list preventive measures against computer viruses;
6. name examples of antivirus programs.

What is antivirus software?

Antivirus software is a program that scans a computer system to detect, prevent and remove threats.

• Main function: to scan, detect, prevent and remove any threat to the computer system.
• Other threats: it also removes other kinds of malicious software, not only viruses.
• Where it works: on computers, laptops and the data stored on them.

What is malware?

Malware is malicious software, which is code that can harm computers, laptops and the data on them.

• Name: the word comes from “malicious software”.
• Computer virus: a type of malware that attaches itself to files or programs and spreads when they are run.
• Harm caused: it can damage files, slow down the computer or steal information.

What are the types of malware?

Common types of malware include viruses, worms, Trojan horses, spyware, adware and ransomware.

How do computer viruses spread?

Computer viruses spread when infected files move from one computer to another.

• Flash drives: an infected flash drive passes the virus to any computer it is plugged into.
• Email attachments: opening an infected attachment can start the virus.
• Downloads: files from unsafe websites may carry malware.
• Networks: some malware moves between computers that are connected together.
• Pirated software: copied programs from unknown sources may contain hidden malware.

What are the signs of a virus infection?

A computer that suddenly behaves strangely may be infected with a virus.

• Slow performance: programs take much longer to open.
• Pop-ups: unwanted windows or adverts appear often.
• Missing or changed files: files disappear, change name or cannot be opened.
• Crashes: the computer restarts or freezes without reason.
• Strange messages: unusual error messages or programs that start on their own.

How does an antivirus work?

An antivirus checks files against known threats, then removes or isolates anything harmful.

1. It scans files, folders, programs and removable drives.
2. It compares them with a list of known malware kept in its database.
3. It also watches for suspicious behaviour in files not on the list.
4. It warns the user when a threat is found.
5. It cleans the file, moves it to quarantine (a safe, isolated place) or deletes it.

What are the types of antivirus scan?

• Quick scan: checks the places where malware is most likely to hide.
• Full scan: checks every file on the computer and takes longer.
• Custom scan: checks only the files, folders or drives the user chooses, such as a flash drive.
• Real-time protection: watches the computer all the time and checks files as they are opened or downloaded.

Why must an antivirus be updated?

• New viruses are created often.
• Updates add the newest threats to the antivirus database.
• An out-of-date antivirus may fail to detect new malware.

How can we prevent computer viruses?

We prevent computer viruses by installing an antivirus and using the computer safely.

1. Install antivirus.
2. Use a secure operating system (OS).
3. Avoid software packages from unknown sources.
4. Always back up your files.
5. Download only from secure sites.
6. Keep the antivirus and the operating system up to date.
7. Scan flash drives before opening their files.
8. Do not open email attachments from unknown senders.

What are examples of antivirus programs?

There are many antivirus programs, and the list below gives some of them.

• Avast
• Avira
• Kaspersky
• McAfee
• PC-Cillin
• F-Secure
• AVG
• Bitdefender Antivirus Plus
• Norton
• Trend Micro
• Webroot Secure
• ESET NOD32
• G-Data Antivirus
• Dr. Solomon toolkit

Evaluation

1. What is an antivirus?
2. State the main function of an antivirus.
3. What is malware?
4. List three preventive measures against computer viruses.
5. Name four examples of antivirus programs.

Assignment

Write a short guide for a new computer user. In it, list five preventive measures against computer viruses and six examples of antivirus programs.