Strengthen your Linux server security: Become proficient with these commands

Enhance the security of your Linux server: Use these commands proficiently

In the current Internet era, servers are important infrastructure that many businesses and individuals rely on. In order to ensure the security of the server, we need to take a series of measures. In addition to configuring firewalls, updating operating systems and software, and using secure passwords, mastering some common commands can also help us monitor and protect servers. This article will introduce some commonly used Linux commands to help you enhance the security of your Linux server.

1. View login log
   The login log is part of server security monitoring. By looking at the login log, we can track the user who logged in to the server and the source. You can view the login log file using the following command:

cat /var/log/auth.log       # Ubuntu
cat /var/log/secure         # CentOS

The login log records each successful and failed login attempt, which can help us discover potential attacks.

2. Monitoring network connections
   Understanding the current network connection status of the server is also the key to ensuring server security. Use the following command to view the current network connection:

netstat -atn   # 查看所有TCP连接
netstat -aun   # 查看所有UDP连接

By viewing the network connection, you can promptly detect abnormal activities, such as a large number of external connections, unknown connections, etc.

3. Find malicious programs
   The existence of malicious programs is an important threat to server security. The presence of malicious software can be discovered through regular scanning. Use the following command to find malicious programs:

find / -name "*.php"     # 查找所有.php文件
find / -name "suspicious_file"    # 查找特定文件

By looking for abnormal files, potential security threats can be discovered and deleted in time.

4. System vulnerability scanning
   Timely patching of system vulnerabilities is also one of the important measures to ensure server security. Use the following command to scan the system for vulnerabilities:

sudo apt update
sudo apt upgrade
sudo apt-get dist-upgrade

The above commands are used to update the software package list, update available software packages and update the release version respectively.

5. Configuring the firewall
   The firewall is the first line of defense to protect the server. It is very important to configure the correct firewall policy. The following command is used to configure the firewall:

ufw enable    # 启用防火墙
ufw allow ssh    # 允许SSH连接
ufw allow http    # 允许HTTP连接
ufw allow https    # 允许HTTPS连接

By configuring firewall rules, you can restrict access to the server and improve server security.

6. Password policy settings
   Strong password policy can greatly enhance the security of the server. Use the following command to set a password policy:

sudo passwd -l username    # 锁定用户账户
sudo passwd -e username    # 强制用户下次登录时修改密码
sudo chage -l username    # 查看用户密码更改信息

By setting a password policy, you can require users to choose more secure passwords and change their passwords regularly.

7. Monitoring system resources
   Monitoring the usage of system resources can help us discover abnormal activities and potential security risks. The following are some commonly used commands:

top    # 查看系统资源使用情况
ps aux    # 查看当前运行的进程
du -h    # 查看磁盘使用情况

By monitoring system resources, abnormal processes, abnormal disk usage, etc. can be discovered in time.

Summary:
The commands mentioned above are only a small part of the improvement of Linux server security. Proficiency in these commands can help us discover and deal with security threats in time. In addition to mastering commands, we should also actively learn the latest security technologies and defense strategies to improve server security. Through continuous learning and practice, we can create a more secure server environment and protect our data and systems from attacks.

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