A computer virus is a type of malware that attaches itself to files, documents, or programs and spreads when the infected content is executed or shared. Viruses remain a useful core concept in cybersecurity because they illustrate how malicious code can replicate, disrupt systems, and create secondary infection paths across devices and users.
What is a Virus?
A computer virus is a malicious program that spreads from host to host. These harmful programs can replicate and spread through files and documents. Viruses have existed for decades. The first virus was created in 1971. Hackers design and distribute viruses to alter the way a computer works. The malware inserts or attaches itself to a legitimate program or document that supports macros to execute its code. A virus causes adverse impacts on computers, such as disrupting regular system operations, logging keystrokes, spamming your email contacts, stealing sensitive information, or destroying data.
Key Takeaways
- A virus is a form of malware that replicates itself and spreads from one host to another through files and documents
- Based on the threat actor’s intentions, a virus can disrupt systems, log keystrokes, spam your email contacts, or corrupt data
- A virus can remain in a target’s device without showing any symptoms of infection
- Specific system and user activities like running an infected program triggers a virus to execute
- You need to be vigilant when surfing the Internet to prevent viruses from getting into your computer
- Install security programs like antivirus, antispyware, and firewall to protect your systems from viruses
How Hackers Use Viruses to Attack Systems
A virus attaches itself to a program, file, or document and stays dormant waiting for specific user and system activities to trigger its code to execute. For instance, a user can trigger a virus by running an infected program on their device. In the current connected world, hackers can infect your computer in many ways. Some of the infection methods include:
- Spreading viruses through text message and email attachments
- Downloading infected files from the Internet
- Social media scam links
- Downloading free games, media players, toolbars, and other system utilities
- Shady mobile app downloads spread viruses to your smartphone
- Downloading and installing software applications without reading the license agreements
- Hackers also disguise viruses as an attachment in commonly shared content like funny images, greeting cards, and video or audio files
What Can a Virus Do to Your System?
A computer virus can adversely affect a system. Some of the malware’s impacts include:
- Infecting other computers in the same network
- Stealing sensitive data, such as passwords
- Logging keystrokes
- Copying files
- Spamming your email contacts
- Taking over control of your computer
Different Types of Computer Viruses
There are different types of viruses, including:
- Boot sector virus – this malicious program executes once you boot your device. A boot sector virus spreads when you plug an infected USB drive into your computer
- Browser hijacker – this virus hijacks some browser functions. For instance, a browser hijacker can redirect you to harmful sites
- Resident virus – the malicious program inserts itself in a computer system’s memory. It executes when you boot an operating system
- Direct action virus – this malware remains dormant and only runs when you execute a file or program containing the virus
- Polymorphic virus – the virus modifies its code every time you execute an infected program or file to evade antivirus detection
- File infector – this virus inserts malicious code into executable files used to perform certain operations in a computer
- Macro virus – hackers create macro viruses in the same language used for software applications.
What are the Signs of a Virus-Infected Computer?
You can tell if your computer has a virus if you notice the following signs:
- Pop-up Windows – frequent pop-up windows can be a sign your device is infected. In most cases, the pop-ups lure you to visit unusual sites or download antivirus programs
- Unsolicited activities on your browser – your browser homepage may introduce other websites, including some that you cannot change
- Mass emails sent from your email account – a virus can access your email contacts, allowing hackers to send emails with your details
- System crashes – frequent system crashes are a sign that a virus has inflicted significant damage on your hard drive
- Slow performance – a sudden change in computer performance is a sign of a virus
- Strange programs starting when you start the computer – your PC might have a virus in case you see an unfamiliar program when you start it, or by checking active applications in the task manager
How Can You Prevent Viruses?
- User awareness – To protect your systems and networks from viruses, you need to be vigilant when surfing the Internet. Avoid downloading files or opening strange links and attachments sent via emails. Carefully evaluate free games and software before installing them.
- Security programs – you can install a trusted antivirus program. Keep your antivirus product updated with the latest virus signatures. Firewalls also monitor incoming and outgoing internet traffic and hide your computer from online scammers.
- File scanning – always scan online files before opening them
- Update your OS and applications – a virus exploits vulnerabilities in your operating system and applications code to infect your systems. Patching your OS and software programs seals the holes and prevents virus code execution
How Can You Remove Viruses from an Infected Computer?
You can use antivirus software to remove computer viruses. The security product allows you to scan to check for viruses in your device.
Virus vs. Worm
A virus usually needs a host file or user action to spread, while a worm can often replicate and move more independently across connected systems or networks.
Frequently Asked Questions
How do viruses usually spread?
Viruses often spread through infected files, email attachments, downloads, removable media, macros, or compromised applications that users execute.
Is every virus ransomware?
No. Ransomware is one specific malware behavior focused on extortion, while viruses are defined more by how they attach and spread.
Related Cybersecurity Terms
