Lesson Notes By Weeks and Term v3 - Junior Secondary 3
Computer Viruses
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Computer Viruses
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Subject: Information Technology (IT)
Class: Junior Secondary 3
Term: 1st Term
Week: 12
Theme: Basic Computer Operations And Concepts
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state the meaning of a computer virus; state types of computer viruses; list examples of computer virus; state sources through which a computer can be in fected state warning signs of a virus; list anti-virus software available for use with a virus.
A computer virus is a type of malicious software (malware) designed to attach itself to legitimate programs, files, or documents and then replicate itself, spreading from one computer to another. Its primary goal is often to interfere with computer operations, corrupt data, or compromise system security without the user's knowledge or permission.
Analogy: Just as a biological virus infects a living organism (like a human body) and causes illness by disrupting normal bodily functions, a computer virus infects a computer system, causing it to malfunction, slow down, or lose data. It cannot exist independently; it needs a host program to spread. This section provides in-depth explanations of the core concepts related to computer viruses, using clear language and examples relevant to the Nigerian context. While "computer virus" is often used as a general term for all malicious software, it's important to differentiate specific types. Viruses, by definition, replicate themselves by attaching to other programs. Other malware types achieve similar malicious goals but use different methods of spread or operation.
Boot Sector Virus: Explanation: This type of virus infects the boot sector of storage devices (e.g., hard drives, USB drives). The boot sector is a crucial part of a storage device that contains the instructions for starting up the operating system. When an infected device is used to boot a computer, the virus loads into memory, infecting the system.
Example Context: A student uses an infected USB drive obtained from a cybercafé to boot their home computer or access files, leading to the infection of the hard drive's boot sector.
File Infector Virus: Explanation: These are the most common types of viruses. They attach themselves to executable files (files that run programs), typically with extensions like `.exe`, `.com`, `.dll`, or `.sys`. When the infected program is run, the virus activates and spreads to other executable files on the system.
Example Context: A user downloads a pirated software application (e.g., a cracked game or video editor) from an untrusted source. This application contains a file infector virus that, upon execution, infects other legitimate programs on the computer.
Macro Virus: Explanation: These viruses infect applications that use macros (small programs embedded within documents), most commonly Microsoft Office applications like Word and Excel. They are embedded within documents (e.g., `.docm`, `.xlsm`) and activate when the document is opened, often prompting the user to "enable macros." Example Context: An email attachment disguised as an official document (e.g., "JAMB Admission List.docm") is opened. If the user enables macros, the virus activates, potentially corrupting other documents or sending itself to contacts.
Polymorphic Virus: Explanation: A polymorphic virus changes its code signature or appearance each time it replicates, making it difficult for traditional antivirus software (which relies on signature detection) to identify and block it. It constantly mutates.
Example Context: An advanced virus that modifies its encryption key and internal structure with each new infection, making it challenging for security software to consistently detect it with the same signature.
Stealth Virus: Explanation: This type of virus attempts to hide its presence from the operating system and antivirus programs. It might intercept system calls to conceal file size changes, memory usage, or other indicators of its activity.
Example Context: A virus that, when an antivirus program scans a file, presents the original, uninfected version of the file, thereby tricking the antivirus into believing the file is clean.
Resident Virus: Explanation: A resident virus installs itself into the computer's memory (RAM) and remains active even after the original host program has finished running. This allows it to continuously infect other programs and files as they are opened or executed.
Non-resident Virus: Explanation: Unlike resident viruses, a non-resident virus does not stay in memory after it has executed. It searches for host programs to infect, infects them, and then becomes inactive.
Trojan Horse (Trojan): Explanation: A Trojan horse is a malicious program that disguises itself as legitimate or desirable software. Unlike a virus, it does not self-replicate. Users are tricked into installing and running it, after which it performs its malicious actions (e.g., creating backdoors, stealing data, giving remote control to attackers).
Example Context: A user downloads a free mobile game or productivity app from an unofficial app store, believing it to be legitimate. The app, unknown to the user, is a Trojan that installs spyware on their phone, stealing bank login details or SMS passcodes.
Worm: Explanation: A worm is a standalone malicious program that replicates itself and spreads across computer networks. Unlike a virus, it does not need a host program to attach itself to; it can spread independently, often exploiting network vulnerabilities. * Example Context: A worm might spread rapidly through a school's local area network (LAN) or across the internet by exploiting a security flaw in an operating system, legitimate. The app, unknown to the user, is a Trojan that installs spyware on their phone, stealing bank login details or SMS passcodes.
Worm: Explanation: A worm is a standalone malicious program that replicates itself and spreads across computer networks. Unlike a virus, it does not need a host program to attach itself to; it can spread independently, often exploiting network vulnerabilities.
Example Context: A worm might spread rapidly through a school's local area network (LAN) or across the internet by exploiting a security flaw in an operating system, consuming bandwidth and bringing down the network.
Spyware: Explanation: Software that secretly observes the user's activities without their permission, gathering information such as browsing history, login credentials, and personal data.
Example Context: A user installs a "free" utility tool for their phone that, unbeknownst to them, also collects their contacts and sends them to a remote server.
Adware: Explanation: Software that automatically displays unwanted advertisements (pop-ups, banners) on a computer or mobile device. While often annoying, some adware can also be malicious by collecting user data or leading to malware installations.
Ransomware: Explanation: A type of malware that encrypts a victim's files or locks their computer, then demands a ransom payment (often in cryptocurrency) in exchange for restoring access to the data or system. * Example Context: A small business owner in Nigeria opens an infected email attachment, and suddenly all their business documents and financial records are encrypted with a message demanding payment to decrypt them.
It is important to note that many well-known "viruses" are actually worms or Trojans, but they are commonly referred to as viruses by the general public.
CIH (Chernobyl): A destructive file infector virus that overwrites critical data on infected systems and BIOS, rendering computers unbootable on specific dates.
I Love You (LoveBug): A highly destructive worm that spread via email in 2000, disguised as a love letter. It overwrote files, stole passwords, and sent itself to all contacts.
MyDoom: A fast-spreading worm that launched denial-of-service attacks and created backdoors. It was one of the fastest-spreading worms in history.
Stuxnet: A sophisticated state-sponsored worm specifically designed to target industrial control systems (SCADA), particularly those used in nuclear facilities.
WannaCry: A notorious ransomware attack in 2017 that affected hundreds of thousands of computers globally, encrypting files and demanding bitcoin payments.
Zeus (Zbot): A Trojan horse malware package that is primarily used to steal banking information through man-in-the-browser keystroke logging and form grabbing.
Sasser: A worm that exploited a vulnerability in Microsoft Windows, spreading rapidly across networks without user interaction.
Understanding computer viruses is not just an academic exercise; it has significant real-world implications for Nigerian citizens and the economy. Personal Data Security and Online Transactions: Many Nigerians now use smartphones and computers for mobile banking, online shopping, applying for JAMB, WAEC, or jobs, and social media. A virus infection can lead to stolen banking details, identity theft, loss of personal photos/documents, or fraudulent transactions, directly impacting an individual's financial stability and privacy. Knowing how to prevent infections protects personal digital assets. Small Businesses and Cybercafés: Small businesses, particularly those relying on computers for inventory, accounting, or point-of-sale systems, are vulnerable. A virus attack can disrupt operations, lead to data loss (e.g., customer records, financial statements), and incur significant costs for repair or data recovery, potentially forcing the business to close. Cybercafes, common in Nigeria, are high-risk environments for virus spread due to shared computers and USB drives; educating users and operators on virus prevention is crucial for their sustainability.
Community Awareness and Digital Literacy: In many Nigerian communities, digital literacy levels vary. Students who understand computer viruses can become informal educators for their families and friends, teaching them about safe browsing, recognizing suspicious emails, and the importance of antivirus software. This can help raise overall community awareness about cybersecurity, reducing vulnerability to scams and attacks. For instance, warning family members about "free recharge card" links or emails from unknown senders.