What are Computer Viruses and How Do They Work?

A computer virus is a specific type of malware designed to replicate and spread by modifying other computer programs and inserting its own code. When this replication succeeds, the affected programs are referred to as “infected” with a computer virus. The sole purpose of any virus is to replicate and spread itself, and damage to the host system is often a consequence of infection.

What are Email Viruses and How Do They Work?

Email viruses, which constitute the majority of computer viruses, consists of malicious code that is distributed in email messages, and it can be activated when a user clicks on a link in an email message, downloads an email attachment or interacts in some other way with the body of an infected email. Virus email are usually programmed to be sent to everyone in the victim's address book once his or her computer has been infected, and tend to proliferate very quickly as a result.

How are Viruses Detected?

As computer viruses have become increasingly problematic, methods of detection have evolved to combat them. There are several different methods that antivirus programs employ to identify viruses, malware and other computer threats. These methods include: Signature-based detection: Traditional antivirus software relies heavily on signature-based detection to identify viruses and malware. In this method, each time a new malware variant is discovered and arrives in the hands of an antivirus company, a signature of the file is extracted and added to the signatures database of the antivirus software. This approach has its limitations, as threat actors have tried to outsmart signature-based antivirus software by creating advanced viruses which modify themselves as a method of disguise to avoid matching existing virus signatures. Heuristics: Heuristic analysis is a popular and effective method for detecting previously unknown viruses, as well as new variants of viruses already in the wild by examining code for suspicious properties. This technique determines the susceptibility of a system to a particular threat using various weighing methods or decision rules. Heuristics analysis is one of the few methods capable of identifying polymorphic viruses. Real-time protection: Real-time protection refers to the automatic protection provided by many antivirus and anti-malware programs, which monitors systems for suspicious activity. Sandbox detection: This behavior-based detection technique runs programs in a virtual environment, logging programs’ actions and behaviors. Depending on the actions logged, antivirus engines that utilize this technique can determine whether a program is malicious or not. This technique has proven to be highly effective, but is rarely used in end-user antivirus solutions due to its slowness. Data mining techniques: In this relatively new approach to virus and malware detection, data mining and machine learning algorithms are used to classify the behavior of a file and determine whether it is malicious or benign depending on a series of features that are extracted from the file.

How to Protect Against Computer Viruses

Antivirus software plays an important role in protecting against email viruses; however, this technology must be implemented as an element of a comprehensive, multi-layered cloud email security solution to effectively combat advanced attacks.

Email Viruses: Prevention Best Practices 2023.

: by MaKenna Hensley; Published: 28 February 2025

Email viruses remain a core cybersecurity threat that is stealing private information, causing data loss, and incurring vast economic losses. Compared to traditional email viruses that work through malicious links and fake messages, cyber criminals now utilize AI-powered tactics to propel attack efficacy.

Individuals and organizations both must understand these threats and embrace advanced practices in email security. Robust cyber-attack prevention is essential, as thousands of malware variants are created daily to compromise email addresses and steal data.

This guide addresses methods through which email viruses spread, evolving cybersecurity threats, and best practices in defending against email threats.

How Email Viruses Work & How to Stay Protected

Email viruses make up a significant portion of cyber threats, spreading through malicious email attachments, links, or embedded code. Once activated, they can steal data, damage systems, and spread rapidly across networks.

How Email Viruses Spread

Hackers employ several methods to disperse email viruses, including social engineering, malicious attachments, and embedded messages.

Phishing attacks: Cybercriminals disguise emails as legitimate messages from trusted sources to trick recipients into clicking malicious links or sharing sensitive information.
Malicious Software: Viruses are hidden in files such as PDFs, Word documents, ZIP archives, and executables (.exe, .js, .scr, etc.), executing when opened.
Embedded email threats: Some viruses run scripts or download malware, typically due to HTML-based exploits, so when an email is opened without clicking links or downloading attachments.

Effective email security controls can prevent infection. However, if an infection does penetrate an email system, its actions will vary based on its function. Some viruses operate covertly in the background, stealing sensitive data or logging keyboard input. Others appropriate system resources to degrade performance. Still others encrypt files to extort money or replicate over networks to infect additional systems.

Stay Protected From Email Viruses

Email viruses are constantly evolving, but strong security practices—such as AI-powered email security tools, verifying senders, avoiding unknown attachments, enabling multi-factor authentication (MFA), and updating security software—can significantly reduce infection risks. However, even with these measures, sophisticated threats remain, capable of stealing sensitive data, encrypting files for ransom, or spreading across networks.

Types of Email Viruses to Know in 2025

Below are the most advanced types of email viruses and how they operate.

AI-Powered Polymorphic Viruses

Unlike traditional malware, computer viruses developed by AI evolve during every infection process by changing their code, making them incredibly hard to detect by traditional antivirus programs. This allows them to evade signature-based defenses and remain undetectable.

Zero-Day Exploits

Hackers are no longer waiting for security holes to be patched—they exploit them as soon as they are discovered. These viruses often arrive in emails disguised as urgent updates or business requests, and they can target specific people or companies with frightening precision. Robust network security measures are essential to defend against such immediate threats.

Ransomware-as-a-Service (RaaS)

Cybercriminals offer RaaS kits for cheap on the dark web, and email is their delivery method. Kits often include customer support and dashboards, making them accessible even to low-skilled attackers. A single click on an attachment can lock down your system until you pay up. Comprehensive cyber attack prevention strategies are necessary to counteract these services.

Viruses Aiming for Your Smart Devices

Your IoT gadgets—smart cameras, thermostats, and even coffee makers—are becoming prime targets. Cybercriminals are using email to sneak malware into the management systems that run these devices. If you assume your smart fridge can’t be hacked, think again. Strengthening your network security can help protect these vulnerable points.

Smarter Keyloggers

Keyloggers used to be clunky spyware that captured every keystroke you made. Now, they’re supercharged with AI, meaning hackers can quickly sift through the data they steal to find personal information: your passwords, credit card numbers, and more. Emails disguised as business documents are popular for getting these onto your system. Implementing secure email practices can reduce the risk of such intrusions.

Deepfake Scams

Deepfake technology isn’t just for creating viral internet videos anymore. Hackers are using it to send eerily convincing emails that look and sound like they’re from your boss, your bank, or even a family member. Once you trust the source, they’ve got you—and the virus hidden in that link or attachment does the rest. Leveraging email encryption can add an extra layer of security against such sophisticated scams.

In 2025, just having an antivirus program and crossing your fingers is simply not enough. Cybercriminals are playing a much more intelligent game, and their targets are everyone from individuals to huge corporations.

The good news? Tools like AI-driven email filters, multi-factor authentication, and regular security updates can help you stay ahead of the curve. Just remember: if it looks suspicious, don't click. All of these risks can be radically lowered by the introduction of secure email best practices and increasing your overall business email security.

Best Email Security Practices to Prevent Cyber Attacks

Here is a list of best practices that will help you protect yourself and your organization:

Email and Link Safety

Avoid clicking links embedded in emails unless verified.
Use link verification tools or malware scanners before opening URLs.
Enable text preview features in your email service to inspect content without clicking.

Attachments and Downloads

Do not open email attachments from unknown or unverified senders.
Avoid opening executable files like .exe, .zip, or .js sent via email.
Use advanced scanners to check attachments for malware, including non-traditional file types like .pdf or .docx.

Software and System Updates

Regularly update your email client, operating system, and web browser.
Ensure antivirus and anti-malware software are up-to-date.

Email Verification and Authentication

Always verify the sender of suspicious emails before taking action.
Double-check requests for sensitive information, financial transfers, or urgent tasks.
Implement multi-factor authentication (MFA) to secure email accounts.

Recognizing and Avoiding Threats

Educate yourself and your team about phishing emails, including AI-generated and deepfake-enabled threats.
Watch for common red flags in emails, such as misspellings, unusual requests, or fake urgency.
Be cautious when sharing your email address online to limit exposure to phishing campaigns.

Email Security Tools

Use AI-driven email security tools to filter phishing emails and detect zero-day threats.
Deploy comprehensive, cloud-based email security solutions with sandboxing and encryption.
Monitor for unusual email activity to detect insider threats.

Responding to Threats

Know how to respond if you click a phishing link: disconnect your device and report it immediately.
Close pop-up ads by using taskbar options—not by clicking the “X” in the ad.

Data Protection

Regularly back up critical data using offline or secure cloud solutions.
Adopt a zero-trust approach to email security, treating every file, link, or sender as potentially malicious.

Staying Ahead of Threats

Stay informed about emerging threats like AI-powered phishing and ransomware trends.
Implement policies and training to raise awareness of modern social engineering tactics.
Verify unexpected email requests through alternative channels, especially if they involve sensitive actions.

To stay ahead of these threats, it's essential to understand the various methods cybercriminals use and how to counteract them effectively. You can significantly reduce your risk exposure by implementing best practices and leveraging advanced security tools.

How to Stop Email Viruses: Your Security Questions Answered

Q: What is signature-based malware detection, and how does it work?

A: Signature-based detection is a traditional antivirus method that scans files by comparing them against a database of known malware signatures. Each time a new virus is discovered, its unique signature is added to the database. This method is effective against well-documented threats but struggles with detecting polymorphic malware—viruses that alter their code to evade detection.

Q: What is real-time protection in email security, and how does it work?

A: Real-time protection continuously monitors your system, scanning for threats as they emerge. Many antivirus programs use this method to provide instant, automated defense against malicious activities before they can cause harm. When combined with threat intelligence and secure email gateways, real-time protection enhances defenses against phishing and emerging cyber threats.

Q: What is sandboxing in cybersecurity, and how does it detect email malware?

A: Sandboxing is a security technique that runs suspicious email attachments or files in a virtual, isolated environment to observe their behavior. If the file performs malicious actions, it is flagged as a threat before it can harm your system. This method is highly effective against zero-day exploits and ransomware but can be resource-intensive, making it more common in enterprise-level cybersecurity solutions.

Q: How do machine learning and data mining detect email viruses?

A: Machine learning and data mining analyze the behavior of files to identify patterns that indicate malicious activity. These AI-driven techniques classify files as safe or hazardous, improving threat detection beyond traditional signature-based methods. By continuously learning from new threats, machine learning enhances protection against phishing and sophisticated email-based attacks.

Q: What is behavior-based malware detection, and how does it stop email threats?

A: Behavior-based detection, also known as heuristic analysis, identifies threats by analyzing how a file behaves rather than comparing it to known malware signatures. This method is crucial for detecting zero-day threats and advanced persistent threats (APTs) that may bypass traditional antivirus software. By flagging suspicious activities, behavior-based detection provides an additional layer of security against evolving cyber threats.

Q: What is a multi-layered approach in email security, and why is it important?

A: No single malware detection method is foolproof. A multi-layered approach integrates various security techniques—such as signature-based detection, real-time monitoring, sandboxing, behavior-based detection, and machine learning—to provide comprehensive protection. This strategy ensures better defense against sophisticated and constantly evolving email-based threats.

How Guardian Digital Can Help

Guardian Digital’s EnGarde Cloud Email Security offers powerful, streamlined protection against email threats such as viruses, malware, spam, and phishing attacks. Its multi-layered security architecture seamlessly blocks malicious messages before they reach your inbox, providing resilient and proactive defense.

Advanced technologies, such as adaptive antivirus engines and heuristics, are built to detect even the most advanced threats, including polymorphic viruses. Strong email encryption ensures your sensitive data is safeguarded, while endpoint protection keeps your systems secure from evolving cyberattacks.

EnGarde is designed for flexibility, eliminating vendor lock-in while delivering robust, customizable security. It's a transparent, collaborative approach that ensures users have complete control and confidence in their email protection.

Centrally managed cloud-based administration simplifies email management, and Guardian Digital’s 24/7/365 customer support means help is always available when you need it. With EnGarde, you get advanced email protection that lets you focus on running your business without worrying about email security.

Keep Learning About Virus and Targeted Threat Protection

Criminals are always finding new ways to exploit weaknesses, making cyber threats constantly evolve. It’s crucial to implement thorough security measures. It is far more effective to prevent email scams from happening in the first place than to deal with them after the fact.

Learn more about protecting your business from malware and ransomware.
Improve your company’s posture to protect against attacks by following best practices for email security.
Keeping the integrity of your email safe requires securing the cloud with spam filtering and enterprise-grade anti-spam services.
Get the latest updates on how to stay safe online.

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Advanced Email Security: Detect & Prevent Email Viruses and Cyber Threats