Definition of a computer virus:

A computer virus is an application that can replicate by inserting its code into other system files. Its mission is to spread from file to file and from computer to computer, primarily causing harm and threatening the integrity of the infected system. Another definition describes it as a program that has the ability to self-replicate, similar to a biological virus, hence its name. A computer virus requires and exploits the operating system, applications, and user identity to perform its actions.

A computer virus is classified as malicious software (malware). To combat computer viruses, antivirus programs and anti-malware scanners are used. Regular updates to the system and applications also help prevent virus infections.

Where do computer viruses come from?

Viruses are typically hidden within commonly used programs, such as games or PDF file viewers. You may also receive an infected file as an email attachment or with another file downloaded from the internet. As soon as you interact with the file (run a program, click on the attachment, or open the file), the virus will automatically activate. The code may then copy itself to other files and make changes to your computer.

How to recognize a virus:

Your internet connection may slow down or even stop working. Another typical symptom is the disabling of antivirus software or firewalls. Infected computers may even begin to operate on their own, performing actions without your knowledge.

How to remove a virus:

Delete all temporary files and run an antivirus scan using antivirus software. If viruses are detected, remove them.

How to prevent viruses:

Avoid programs from unknown sources.

Do not open attachments from unwanted emails or Facebook messages.

Download applications only from official app stores (e.g., Google Play for Android).

Introduction:

The most dangerous computer viruses

To determine which viruses are the most dangerous, they must first be categorized. The basic categories of viruses include those that replicate and damage files, but they only attack when activated by a program, typically with the ".exe" extension.

Examples of computer viruses:

• File viruses

• Macro viruses

• Mainboard viruses

• Cluster viruses

• Intruder viruses

• Multilayer viruses

Computer viruses can also be classified based on their speed of operation:

Fast viruses: These viruses aim to infect the system as quickly as possible by infecting every file in the shortest time. The virus's activity is usually noticeable due to delays and anomalies in the operating system's performance.

Slow viruses: These viruses work in such a way that the user cannot detect that the computer is infected. They use variable encryption procedures and hiding techniques, making them difficult to detect – even high-quality antivirus programs often fail to identify them.

Other types of malicious software

Worms – A computer worm

A worm is a self-replicating program that spreads independently, unlike a virus that requires a host file.

Wabbit

A resident program called Wabbit does not replicate over the network. It performs a specific operation, such as consuming computer memory by duplicating files until the system runs out of space.

Trojan horse (also called a Trojan) is software that disguises itself as interesting or necessary applications. At the same time, the Trojan installs unwanted elements, such as spyware programs, logic bombs, or backdoors, allowing unauthorized individuals to control the system.

Backdoor is a vulnerability in the system designed to be used later. A virus may have been left by a cracker who exploited another software vulnerability for this purpose.

Stealware is designed to steal from unsuspecting users, often used for fraud, such as internet payment scams. The virus replaces the account number to which a payment should be transferred.

Adware is a type of free software license that includes displaying ads. The publisher earns money by displaying ads, usually banners, and it is often used in apps that connect to the internet.

Browser Hijacker (Browser Helper Object) modifies browser settings without the user's consent. It can change the homepage, error page, or search page. These programs often take personal data. During installation, users are usually asked for consent to install the program, which they often overlook.

Exploit uses errors in software, taking control of processes and machine code.

Rootkit is a tool that enables system intrusions. The virus infects the kernel and removes hidden programs from the process list, potentially hiding other viruses, including Trojans.

Keylogger is software designed to steal passwords and data. Sometimes it's used by employers to monitor employee activity.

Ransomware is one of the most dangerous programs for regular users. It can change the page you are viewing (often banking pages), display warning messages about the page being blocked, and demand money in exchange for access.

Additional threats in the network

Phishing is a type of fraud where attackers impersonate another person or institution to deceive victims into providing sensitive information or taking specific actions.

Pharming is one of the most dangerous forms of phishing. Even if you enter the correct website address, you are redirected to a fake one that looks identical to the original. Its goal is to steal login credentials, passwords, or credit card numbers.

SMS phishing is a social engineering attack involving sending SMS messages with manipulated content aimed at tricking users into specific actions, such as calling a premium-rate number or sending a premium SMS.

Spam refers to unwanted and unnecessary electronic messages, often distributed in bulk via email or messaging platforms. Its essence is spreading a message to a large group or sending manipulated links that, when clicked, infect the user's computer or phone.

Prevention and counteraction of computer viruses

It is much easier to take preventive measures to ensure that no virus appears on your computer, laptop, or phone than to spend time removing one later. Moreover, a virus may destroy files and documents in such a way that they cannot be recovered. So, how can you effectively defend against viruses entering your system?

Hacktivists – who are they?

Hacktivists have been active worldwide since 2003, conducting many high-profile operations. The most well-known hacktivist group is Anonymous. For a long time, this group fought against ISIS, individuals and institutions supporting the ACTA agreement, targeted child pornography websites, and even fought against drug cartels. Another well-known group is Chaos Computer Club, a true team of hacktivists. They have stolen personal data, money, and passwords, and then, seemingly without consequence, returned them to their victims. The aim was to educate internet users who often do not consider the consequences of their online actions. On the other side of the spectrum, there was Lizard Squad, which admitted to attacking the Malaysia Airlines website and disrupting Facebook. They were most known for their disruptive DDoS attacks against PlayStation Network servers, Xbox Live, and League of Legends. Fortunately, some hackers were captured by law enforcement and imprisoned. Throughout history, there have also been state-sponsored groups. One of them is the Syrian Electronic Army, made up of Iranians, which was formed to support Bashar al-Assad. Among their targets were Barack Obama and Nicolas Sarkozy. Phishing and DDoS attacks were among their preferred methods.

Examples of hacktivist actions

In 2006, the Anonymous group stole the source codes of Norton AntiVirus and Norton Internet Security. Six years later, they published them online as retaliation for the arrest of LulzSec members.

2011 was a very intense year for Anonymous. It included, among other things, the announcement of Operation Blitzkrieg, targeting fascists and nationalists. The group successfully blocked websites and forums where these groups communicated. They also published thousands of personal data of individuals involved in these organizations.

In 2011, Sony clashed with a hacker who cracked PlayStation 3 security, leading to a massive attack on PlayStation Network. The DDoS attack was so severe that it not only stole data from 77 million users (including credit card details) but also disrupted PlayStation Network services for weeks. This created a major public relations crisis for Sony.

In 2012, people protested in the streets against the introduction of the ACTA law, which was essentially intended to control online content. The Anonymous group was actively involved in fighting this law—blocking, for example, the website of Prime Minister Donald Tusk in Poland.

In 2016, during the US presidential elections, representatives of Anonymous also took action, declaring war on Donald Trump for his "hate-filled campaign" and also Hillary Clinton. The hacktivist movement became divided, with some suggesting that both voices should be heard.

To effectively defend against a virus, we should use:

Antivirus programs designed to recognize and eliminate viruses.

Programs that remove adware and spyware, which may have not been detected by antivirus programs or which the user may have unknowingly agreed to install.

Ad-blocking add-ons, such as Adblock and Adblock Plus.

Programs for backing up important files or entire disks.

The option to store files online in "the cloud."

Additionally:

Carefully read the messages displayed during program installation.

Download programs and applications only from trusted websites.

Regularly update installed software, especially the operating system.

Regularly scan disks with antivirus software.

Do not open email attachments from unknown senders.

Do not click on pop-up ads or notifications about winnings.

Your task will be to prepare a presentation on a chosen topic related to computer viruses.

Your task is to:

Identify the types of computer viruses,

Determine methods to prevent the spread of computer viruses,

Prepare a multimedia presentation on computer viruses, agreed upon with the teacher.

You will work in 4 groups, each preparing a presentation on a different topic. This way, you will learn many important aspects of computer viruses, not only from your own presentation but also from the presentations prepared by the other groups. You will then present your work together to the class.

When preparing materials, remember that you must collaborate not only within your group but also between groups—otherwise, you will not be able to prepare a presentation that broadens your knowledge of computer viruses.