A computer virus is a program capable of duplicating itself by attaching to a legitimate file or software. When this file is opened, the malicious code executes and can spread to other elements of the system. This simple definition covers a broader reality: current threats go beyond the classic virus and include ransomware, spyware, or Trojans, grouped under the term malicious programs (malware).
Cyber Resilience Act: what the European regulation changes for your devices
The European regulation on cyber resilience (Cyber Resilience Act, or CRA), which came into effect on December 10, 2024, fundamentally changes the obligations of manufacturers. All products containing digital elements sold in the European Union (computers, smartphones, connected objects, consumer software) are affected.
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Manufacturers will have to ensure security updates throughout the expected lifespan of the product, manage vulnerabilities in a documented manner, and implement an incident reporting mechanism. From December 11, 2027, these requirements will be fully applicable, with mandatory CE marking and notification of actively exploited vulnerabilities.
In practical terms, a device purchased new after this date will need to receive security patches without the user having to manually search for updates. This is a paradigm shift: the responsibility for initial protection shifts to the manufacturer. Specialized resources like viruslab.fr allow tracking the evolution of these obligations and comparing security solutions suitable for each type of device.
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This regulation does not exempt the user from vigilance. It establishes a foundation, not a complete shield.
Attack surface: understanding the entry points of malicious programs
Before choosing an antivirus or configuring a firewall, it is essential to identify how a threat enters. The attack surface refers to all the points through which a malicious program can access a device. The larger this surface, the greater the risk.
On a computer, the main vectors remain email (malicious attachments, phishing links), downloads from unofficial sources, and infected USB devices. On a smartphone or tablet, applications installed outside official stores and connections to unencrypted public Wi-Fi networks add additional vectors.
Reducing this surface in practice
- Uninstall unused applications and software: each program present on a device represents a potential entry point, especially if it no longer receives updates
- Disable unused communication protocols (Bluetooth, NFC) when not in use, to limit unsolicited connections
- Check the permissions granted to mobile applications: a flashlight app requesting access to contacts and the microphone indicates suspicious behavior
- Prioritize the encryption of data stored on the device, a native option on most recent systems
Reducing the attack surface is an ongoing process, not a one-time action.
Antivirus and firewall: two complementary layers of protection
A antivirus software scans the files present on a device and those that transit through it. It compares their signature to a database of known threats and, in recent versions, uses behavioral analysis to detect previously unlisted malware.
The firewall operates at another level: it filters incoming and outgoing network connections. A malicious program attempting to send stolen data to a remote server will be blocked if the firewall is correctly configured. The antivirus protects files, the firewall protects network traffic.
What the antivirus does not cover
No antivirus detects all threats. Phishing attacks rely on user manipulation, not on an infected file. A fraudulent link leading to a fake banking login page does not necessarily trigger an alert.
Similarly, so-called “zero-day” vulnerabilities (flaws unknown to publishers) inherently escape signature databases. This is precisely why protection relies on multiple layers and not on a single tool.
System and software updates: the often-overlooked link
Applying security updates for the operating system and installed software fixes vulnerabilities exploited by malicious programs. An unpatched known vulnerability remains the easiest target for an attacker.
Modern operating systems offer automatic updates. Disabling them to avoid a restart exposes the device for the entire duration of the delay. On mobile devices, the situation is more mixed: some manufacturers stop providing patches after a few years, which the Cyber Resilience Act aims to regulate starting in 2027.
Third-party software (browsers, PDF readers, office suites) deserves the same attention. An outdated browser is a frequent infection vector, as it interprets potentially malicious web content on every visited page.
Backups and segmentation: limiting damage after an infection
Protection is not just about preventing intrusion. Ransomware that encrypts an entire hard drive renders data inaccessible, even if the device is later cleaned. Without a recent backup, the loss can be permanent.
- Maintain at least one backup copy on a medium physically disconnected from the device (external drive, dedicated USB stick) so that ransomware cannot encrypt it along with the main system
- Use a user account without administrative rights for daily tasks, to limit a malicious program’s ability to modify the system
- Separate personal and professional uses on distinct sessions or devices to prevent an infection on one from compromising the other
Segmentation reduces the impact perimeter. A virus that reaches an account without administrative privileges cannot install a driver or modify system files.
Device protection relies on stacking complementary measures, not a single solution. Regulation, attack surface reduction, security software, updates, and backups form a set where each layer compensates for the limitations of the others. Removing one link weakens the entire chain.