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SNORT3 Snort is an open source network intrusion detection system capable of performing real-time traffic analysis and packet logging on IP networks。It can perform “protocol analysis,” “content search,” and “matching,” and can be used to detect various attacks such as “buffer overflows,” “stealth port scans,” “CGI attacks,” “SMB probes,” “OS fingerprinting attempts,” “semantic URL attacks,” and “server message block probes. The system can be used to detect a variety of attacks, such as

1.Disabling SELinuxFirst, disable selinux. selinux is a feature that improves auditing and security in Linux, but when enabled, it places considerable restrictions on the behavior of services and on what can be configured. Therefore, it is basically disabled in many cases.SELinux operating modesEnforcing : SELinux functionality is enabled and access control is enabledPermissive : SElinux will warn, but no access restrictions will be placeddisabled : Both SElinux function and access control are disabled2.System ModernizationPackage updates are performed as soon as possible immediately after OS installation.However, when a dnf update is performed, a kernel update is also performed at the same time.A kernel update may require rebooting the system or stopping services, or worse, a kernel panic may occur and the system may not boot. It is wiser to exclude the kernel from the update.The kernel can be excluded from updates by running dnf -y update with "--exclude=kernel*" after it.

1.Remote connection via SSHSSH is a service for connecting remotely to a server and is basically running immediately after the OS is installed, but the default settings are somewhat insecure.Here we will configure the default settings to increase the security of ssh connections.1.1 Edit SSH service configuration fileModify the configuration file to change the SSH service settings.The SSH service configuration file is "/etc/ssh/sshd_config".2.Firewall (firewalld) settingsThe firewall is set to firewalld as default and is enabled during OS installation.4.NTP ServerBuild an NTP server to synchronize the server time with Japan Standard Time

SSH connection with authentication using public key cryptography Creation of public and private key pairsCreate a public/private key pair for a user connecting to the Linux server using OpenSSH.Use ssh-keygen to create key pairs.Creation of public/private key pairs is performed with remote login user privileges。If you do not specify the destination and file name, id_ed25519 and id_ed25519.pub will be created in /home/(user name)/.ssh/. On the way, enter the password for the key.