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SSH connection with authentication using RSA public key cryptography Creation of public and private key pairs Create a public/private key pair for a user connecting to a Linux server using OpenSSH.Use ssh-keygen to create the key pair.This time, we will create a key set using the RSA cipher used in the SSH protocol Version 2.Creation of public/private key pairs is performed with remote login user privileges (huong).If you do not specify the destination and file name, id_rsa and id_rsa.pub will be created in /home/huong/.ssh/. On the way, enter the password for the key.

1. Setting up remote connection by 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 SSH service configuration file changesModify the configuration file to change the SSH service settings.The SSH service configuration file is "/etc/ssh/sshd_config".

1. Install bash completion extension package# dnf -y install bash-completion# reboot2. Disable 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.

OracleLinux8.6  InstallOracle Linux provides a 100% application binary compatible alternative to Red Hat Enterprise Linux and CentOS Linux for both hybrid and multi-cloud environments.Since 2006, Oracle Linux has been completely free to download and use. Source code, binaries and updates are provided free of charge. It is freely redistributable. Free for use in production environments.This time, we will proceed with Oracle Linux 8.6 because the latest Oracle Linux 9.0 does not yet have sufficient software.

1.Website data backup1-1.Backup under /var/www/html①Create backup script file2.MySQL database backup①Create backup script file# cd /var/www/system# vi db_my_backup.sh3.Restore backup files under html① Store HTML backup files in "/ (root)" directory# cd /var/www/backup/html_bak# cp html_back_20220610.tar.gz / ←Specify the backup file with the latest date4.Restore Mysql backup file①Save the database backup file to any directory and（In the example, the directory is "/var/www/backup/db_bak".）Extracting data# cd /var/www/backup/db_bak

Tripwire1.Download and installation# cd /usr/local/src# wget https://rpmfind.net/linux/epel/9/Everything/x86_64/Packages/t/tripwire-2.4.3.7-13.el9.x86_64.rpm# rpm -Uvh tripwire-2.4.3.7-13.el9.x86_64.rpmChkrootkit①Download and install chkrootkit# cd /usr/local/src# wget https://launchpad.net/chkrootkit/main/0.55/+download/chkrootkit-0.55.tar.gz# tar xvf chkrootkit-0.55.tar.gzLogwatch①Install# dnf install logwatchIntroduce disk usage check script1. Script Creation# cd /var/www/system# vi disk_capacity_check.sh

 SuricataSURICATA IDS/IPS is an open source IDS that monitors communications on the network and detects suspicious traffic.The basic mechanism is signature-based, so it can detect predefined unauthorized communications. Suricata is also characterized by its ability to provide protection as well as detection.1.advance preparation①Activate the EPEL RepositorySNORTSnort is an open source network intrusion detection system that can perform 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 a variety of attacks such as buffer overflows, stealth port scans, CGI attacks, SMB probes, OS fingerprinting attempts, semantic URL attacks, and server message block probes. detection.

1.SSL Certificate Acquisition ( Let's Encrypt )Install the latest open ssl# dnf install openssl-devel1.1 advance preparation1.Package management system Snappy installationSince the SSL certificate issuing tool "certbot" of Let's Encrypt is recommended to be installed using "snap" after 2021, install Snapd first.(Can also be installed the traditional way with dnf or yum)2. Converting Apache to httpsInstall the following# dnf -y install mod_ssl3. SSL/TLS (Let's Encrypt) settings on the mail server3.1 Obtaining a certificate for the mail serverObtain a certificate for the mail server, but it cannot be obtained in the same way as above, so the following with the "--standalone" option fails.

Clamav(anti-virus)1.Clam AntiVirus install# dnf -y install clamav clamd clamav-updateMail Server Installation1. Postfix1.1 InstallInstall Postfix and build an SMTP serverMail server : Postfix + Clamav + Amavisd+SpamAssassin1.Real-time scanning of e-mails①Install Amavisd and Clamav Server

1.FTP Server1.1vsftpd Install# dnf -y install vsftpd1.2vsftpd configurationSave the unedited vsftpd.conf with .bak# cp /etc/vsftpd/vsftpd.conf /home/huong/vsftpd.conf.bak2. vsftpd SSL/TLSConfigure Vsftpd to use SSL/TLS2.1 Create self-signed certificatesThis work is not required if you are using a trusted, legitimate certificate such as Let's Encryp3. File server installation with SambaBuild a file server with access rights that requires user authentication with Samba.Installation Procedure①Create shared folders with access rights that require user authentication②Accessible group creation③Creation of users belonging to accessible groups④Configuration File Edit

SSH connection with authentication using public key 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.

1.Setting up a 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.2.Firewall (Firewalld) settingsIn Oracle, the firewall is firewalld configured by default and enabled during OS installation.To briefly explain "firewalld," when setting communication control policies, communication permission/blocking rules are applied to predefined zones, and these zones are then assigned to each NIC (network adapter).

1.Install bash completion extension package# dnf -y install bash-completion# reboot2.Disabling SELinuxFirst, disable selinux.　selinux is a feature that improves auditing and security in Linux, but when enabled, it can limit the behavior of services and the contents of the configuration considerably.Therefore, it is basically a case of invalidation 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 disabled

OracleLinux9.2Oracle Linux provides a 100% application binary compatible alternative to Red Hat Enterprise Linux and CentOS Linux for both hybrid and multi-cloud environments.Since 2006, Oracle Linux has been completely free to download and use. Source code, binaries and updates are provided free of charge. It is freely redistributable. Free for use in production environments.今回は、最新のOracle Linux9.2(2023年5月リリース)で進めていきます。This time, we will proceed with the latest Oracle Linux 9.1.(May 2023 Release)１．Oracle Linux9.2 DownloadOracle Linux 9.2 installation image (OracleLinux-R9-U2-x86_64-dvd.iso ) can be downloaded from the following sitehttps://www.oracle.com/linux/