Is Antivirus Necessary for Ubuntu? The Truth Behind the Security Myth and the Best Protection Measures

By 佐川 直弘 | Naohiro Sagawa (運営者)

※記事内に広告を含みます。Amazonアソシエイトとして適格販売により収入を得ています。　

1. Introduction

Ubuntu is one of the most widely used Linux distributions worldwide. Due to its high stability and open-source nature, it is utilized by a broad range of users, from individuals to enterprises and server environments. However, many Ubuntu users believe that “Linux is immune to viruses.”

In this article, we will thoroughly explain the risks of viruses on Ubuntu and provide essential information on how to take appropriate countermeasures. We will discuss whether antivirus software is necessary, recommend security measures, and explain how to keep your Ubuntu environment secure.

Is Linux Really Immune to Viruses?

1.1. Why Linux is More Resistant to Viruses Than Windows

• Strict Permission Management
  On Linux, general users cannot modify critical system files without root (administrator) privileges. This significantly reduces the risk of malware affecting the entire system.
• Package Management System
  In Ubuntu, software installation is recommended through official repositories (APT). This minimizes the risk of unauthorized software being installed.
• Fewer Malware Targeting Linux
  Looking at the global OS market share, Windows users are overwhelmingly more numerous. Attackers tend to create malware targeting Windows because it allows them to reach a larger number of targets. As a result, viruses specifically designed for Linux remain relatively scarce.

Why You Still Need Virus Protection

However, assuming that “Linux is completely safe” is a dangerous misconception. Even in Ubuntu, the following risks exist:

• Phishing Attacks Through Web Browsers
  Even when using Ubuntu, there is a risk of visiting malicious websites through Chrome or Firefox and accidentally downloading malware.
• Malicious Scripts and Malware
  There has been an increase in malware specifically targeting Linux, such as rootkits and ransomware. Server administrators, in particular, should be cautious.
• Spreading Viruses to Other OSs
  Even if Ubuntu users are not affected themselves, they may unknowingly transmit viruses to Windows users when sharing files. For example, an email attachment received on Ubuntu might contain Windows malware, which could infect another system upon being forwarded.

Article Structure

In this article, we will thoroughly cover Ubuntu virus protection in the following structure:

1. Current state of viruses on Ubuntu
2. Necessity of antivirus software
3. Recommended antivirus software
4. Security measures beyond antivirus
5. FAQ (Frequently Asked Questions)
6. Conclusion

We will explain everything in a clear and accessible manner to help you enhance Ubuntu’s security, so please read until the end.

2. The Current State of Viruses on Ubuntu

Ubuntu, as a Linux distribution, is known for its high security. However, assuming that “Ubuntu cannot be infected by viruses” is incorrect. In recent years, malware targeting Linux has been increasing, and even Ubuntu users need to remain vigilant.

2.1. Risk of Virus Infections on Linux

Fewer Viruses Compared to Windows

Compared to Windows, the overall risk of virus infections on Linux is lower. The reasons include:

• Market Share Differences
• Windows holds over 70% of the global desktop OS market share, whereas Linux desktop users make up only about 2–3%. This makes Linux a less attractive target for attackers.
• Permission Management
• On Linux, system files cannot be modified without root (administrator) privileges. Even if malware infiltrates the system, the risk of it taking over the entire system is significantly lower.
• Software Management System
• Most applications on Ubuntu are provided through official repositories, ensuring that software installations come from trusted sources. By avoiding downloads from unverified sources, the chances of malware intrusion are significantly reduced.

2.2. Emerging Threats Targeting Ubuntu

The number of malware programs targeting Linux, including Ubuntu, is indeed increasing. Notable threats include:

• Ransomware for Linux
• Recently, ransomware like RansomEXX has been targeting Linux systems, particularly corporate server environments, encrypting data and demanding ransoms.
• Trojan Malware for Linux
• Malware such as Ebury infiltrates Linux systems via SSH connections and creates backdoors, posing a significant threat to remote server administrators.
• Rootkits
• Rootkits like Rootkit.Linux.Snakso can hide within the Linux kernel and allow unauthorized access. Detecting them is challenging, making it crucial to monitor system abnormalities.
• Cryptojacking (Unauthorized Mining)
• Cybercriminals hijack compromised systems to mine cryptocurrency. Cases of infected Linux servers running unauthorized mining processes have been rising.

2.3. Infection Pathways and Risks

Although Ubuntu is considered more resistant to malware, it is still vulnerable through certain infection pathways, including:

• Phishing Attacks via Web Browsers
• Even on Ubuntu, users should be cautious of phishing attempts through Chrome or Firefox that lure them into downloading malware.
• Email Attachments and Malicious Links
• Malicious scripts can be distributed via email attachments, such as .sh (shell scripts) or executable files hidden inside .zip archives.
• PPA and Third-Party Repositories
• Although official repositories (APT) are recommended, some software is only available via third-party repositories (PPAs). Adding untrusted PPAs may expose the system to malware.
• USB Devices and External Storage
• Even on Ubuntu, USB flash drives and external hard drives can be infection vectors, especially when used interchangeably with other OSs like Windows or macOS.

2.4. Key Points for Ubuntu Users

• Install Software Only from Trusted Sources
• Use Ubuntu’s official repositories and be cautious when adding PPAs.
• Avoid Clicking Suspicious Email Links or Attachments
• Verify the sender and destination URL before opening links in emails.
• Strengthen SSH Security
• If using SSH, disable password authentication and use key-based authentication instead.
• Keep Your System Updated
• Apply security updates regularly to prevent vulnerabilities.
• Conduct Regular Virus Scans
• Use antivirus tools like ClamAV or Sophos to scan your system periodically.

2.5. Summary

Ubuntu is more resilient to viruses than Windows, but it is not invincible. Recently, malware targeting Linux has been increasing, so users must take necessary precautions.

3. Is Antivirus Necessary for Ubuntu?

Linux-based operating systems, including Ubuntu, are generally considered less prone to viruses compared to Windows. However, attacks targeting Linux have been rising, making it risky to assume that “Ubuntu does not need antivirus protection.”

This section will explore whether Ubuntu users need antivirus software and who should consider installing it.

3.1. How to Determine If You Need Antivirus Software

Not all Ubuntu users need to install antivirus software. The necessity depends on the usage environment and purpose. Below, we summarize cases where antivirus software is recommended and cases where it may not be necessary.

Cases Where Antivirus Software is Recommended

✅ 1. Frequent File Sharing with Other OSs (Windows/macOS)

• Even if Ubuntu is not directly affected, it can act as a carrier for Windows-targeted viruses.
• If you frequently share files via USB drives or email with Windows users, running virus scans can help prevent spreading infections.

✅ 2. Using Ubuntu in Corporate or Server Environments

• If you use Ubuntu within a corporate network, a virus infection could affect the entire organization.
• Especially for web servers, file servers, and mail servers, installing antivirus software helps prevent malware from spreading.

✅ 3. Allowing External SSH Access to Ubuntu

• Exposing SSH to the internet increases the risk of brute-force attacks and malware intrusion.
• As Linux-based backdoor malware is on the rise, antivirus software can help with intrusion detection and scanning.

✅ 4. Installing Untrusted Third-Party Software

• Using software outside of the official repository (PPA, third-party packages) increases the risk of installing malicious code.
• There have been past cases where malicious PPAs compromised system security.

✅ 5. Frequent Use of Public Wi-Fi

• Public Wi-Fi networks are susceptible to sniffing (data interception) by attackers.
• Although Ubuntu itself is secure, antivirus software can help protect against network-based threats.

Cases Where Antivirus Software May Not Be Necessary

❌ 1. Minimal Internet Usage

• If the system is not connected to a network and no external data transfers occur, the risk of infection is extremely low.

❌ 2. Only Installing Software from Official Repositories

• If you strictly use software from Ubuntu’s official repositories without adding external PPAs or downloading third-party applications, the risk of infection is nearly zero.

❌ 3. Personal Use Without File Sharing Across OSs

• If you use Ubuntu as a standalone OS without sharing files with Windows or macOS, antivirus software is generally unnecessary.

3.2. Security Measures Beyond Antivirus Software

Even without installing antivirus software, Ubuntu users can achieve strong security by properly configuring system settings.

Keeping the System Updated

• Regular system updates are the most important factor in maintaining security.

sudo apt update && sudo apt upgrade -y

• Kernel updates

sudo apt dist-upgrade -y

Enabling UFW (Uncomplicated Firewall)

• Using UFW helps block unnecessary network connections and prevent external attacks.

sudo ufw enable
sudo ufw allow ssh
sudo ufw status

Closing Unused Ports

• Leaving unused ports open can expose your system to potential attacks.

sudo ss -tulnp

Using AppArmor

• Ubuntu includes AppArmor, a security tool that restricts application behavior to minimize malware impact.

sudo aa-status

3.3. Summary

While Ubuntu has a lower risk of virus infections than Windows, antivirus software may still be necessary depending on the use case. In particular, users who frequently share files with other OSs or manage servers should consider security measures.

At the same time, antivirus software is not always required. Keeping your system updated and configuring a firewall properly can provide sufficient protection.

4. Recommended Antivirus Software

While Ubuntu is less susceptible to viruses than Windows, antivirus software may be necessary for scenarios such as server management, file sharing, or external network connections. Here are some recommended antivirus solutions for Ubuntu.

4.1. List of Antivirus Software for Ubuntu

The table below summarizes available antivirus software for Ubuntu.

Note: Many Linux antivirus solutions have been discontinued over time.

4.2. ClamAV: Open-Source Virus Scanner

ClamAV is one of the most widely used antivirus solutions for Ubuntu. It is lightweight, open-source, and suitable for server use.

ClamAV Features

• Completely free
• Operates via CLI (Command Line Interface)
• Supports scheduled scans
• Detects Windows viruses as well

Installing ClamAV

sudo apt update
sudo apt install clamav clamav-daemon -y

Updating Virus Definitions

sudo freshclam

Running a Virus Scan

clamscan -r --remove /home/user

4.3. Chkrootkit: Detecting Rootkits

Chkrootkit is a tool specialized in detecting rootkits, a type of malware that hides within a system and grants unauthorized access.

Installing Chkrootkit

sudo apt install chkrootkit -y

Running a Rootkit Scan

sudo chkrootkit

5. Security Measures Beyond Antivirus

Installing antivirus software is important, but it is not enough. To prevent infections, you should also configure basic security settings.

(The next section will cover firewall settings, SSH security, AppArmor, and system updates.)

5.1. Configuring and Managing the Firewall (UFW)

The firewall is a crucial security feature that prevents unauthorized external access. Ubuntu comes with a simple yet powerful firewall tool called UFW (Uncomplicated Firewall).

Enabling and Configuring UFW

Enabling UFW blocks unwanted external connections. Use the following command to activate UFW:

sudo ufw enable

Check the current status:

sudo ufw status verbose

To allow specific ports (e.g., SSH on port 22):

sudo ufw allow ssh

To block all incoming connections and allow only necessary ones:

sudo ufw default deny incoming
sudo ufw default allow outgoing

To allow SSH connections only from a specific IP address:

sudo ufw allow from 192.168.1.10 to any port 22

To disable UFW if necessary:

sudo ufw disable

Since UFW is both simple and effective, it is highly recommended to keep it enabled by default.

5.2. Strengthening SSH Security

SSH (Secure Shell) is commonly used for remote administration of Ubuntu servers. However, leaving the default settings can make your system vulnerable to brute-force attacks. Here are some security measures:

Disable Password Authentication and Use Key Authentication

Edit the SSH configuration file:

sudo nano /etc/ssh/sshd_config

Modify or add the following line to disable password authentication:

PasswordAuthentication no

Restart SSH to apply the changes:

sudo systemctl restart ssh

This prevents attackers from guessing passwords through brute-force attacks.

Using Fail2Ban to Prevent SSH Attacks

Fail2Ban automatically detects brute-force login attempts and blocks the attacking IP address.

Install Fail2Ban:

sudo apt install fail2ban -y

Edit the Fail2Ban configuration file:

sudo nano /etc/fail2ban/jail.local

Add the following settings:

[sshd]
enabled = true
port = ssh
maxretry = 5
bantime = 600

Restart Fail2Ban:

sudo systemctl restart fail2ban

This configuration blocks an IP address for 10 minutes if it fails to log in five times.

5.3. Using AppArmor for Enhanced Security

AppArmor is a security feature in Ubuntu that restricts the behavior of applications to minimize the impact of malware.

Check AppArmor Status

sudo aa-status

Restrict Application Behavior

For example, to enforce security policies on Firefox:

sudo aa-enforce /etc/apparmor.d/usr.bin.firefox

AppArmor is particularly useful for server environments and systems requiring high security.

5.4. Keeping Your System Up-to-Date

Keeping Ubuntu updated is essential for security, as updates often include patches for vulnerabilities.

Update the Entire System

sudo apt update && sudo apt upgrade -y

Upgrade the Kernel

sudo apt dist-upgrade -y

Enable Automatic Security Updates

1. Install unattended-upgrades:

sudo apt install unattended-upgrades -y

2. Enable automatic updates:

sudo dpkg-reconfigure --priority=low unattended-upgrades

This ensures security updates are automatically applied.

5.5. Security Checklist

Use this checklist to verify your Ubuntu security settings:

✅ Is the firewall (UFW) enabled?
✅ Is SSH password authentication disabled in favor of key authentication?
✅ Is Fail2Ban installed to protect against brute-force attacks?
✅ Are system updates applied regularly?
✅ Are unnecessary ports and services closed?
✅ Have you avoided adding untrusted PPAs?
✅ Have you set browser security measures (HTTPS enforcement, NoScript)?

5.6. Summary

To secure Ubuntu, simply installing antivirus software is not enough. Basic security configurations must be applied as well.

6. FAQ (Frequently Asked Questions)

6.1. Does Ubuntu come with built-in antivirus software?

A: No, Ubuntu does not include built-in antivirus software. However, its strict permission management and secure package management system make it less susceptible to viruses. Nevertheless, depending on usage, antivirus software may be useful.

6.2. Is Ubuntu safer than Windows?

A: Generally, Ubuntu and Linux systems are considered more secure than Windows due to:

• Fewer viruses targeting Linux
• Strict permission controls
• Secure software package management
• Built-in firewall (UFW) enabled by default

However, assuming that “Ubuntu is completely safe” is dangerous. Linux-targeting malware is increasing, and security best practices must be followed.

7. Conclusion

This article has covered whether Ubuntu needs antivirus protection and provided detailed security measures.

7.1. Key Takeaways

✅ Ubuntu is more secure than Windows but not invulnerable
✅ Antivirus software may be needed in specific cases (file sharing, server use)
✅ Basic security measures (firewall, SSH security, updates) are essential

7.2. Final Recommendations

• For personal use: Keep your system updated and enable the firewall.
• For server management: Enhance SSH security and use Fail2Ban.
• To prevent spreading Windows malware: Run virus scans with ClamAV.

By understanding Ubuntu’s security features and implementing appropriate measures, you can ensure a safe computing environment.