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1.Setting up a remote connection via SSH SSH 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) settings In 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).

Creation of public and private key pairs Create 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.FTP Server 1.1vsftpd Install # dnf -y install vsftpd 1.2vsftpd configuration Save the unedited vsftpd.conf with .bak # cp /etc/vsftpd/vsftpd.conf /home/huong/vsftpd.conf.bak 2. vsftpd SSL/TLS Configure Vsftpd to use SSL/TLS 2.1 Create self-signed certificates This work is not required if you are using a trusted, legitimate certificate such as Let's Encryp 3. File server installation with Samba Build a file server with access rights that requires user authentication with Samba. Installation Procedure ①Create shared folders with access rights that require user authentication ②Accessible group creation ③Creation of users belonging to accessible groups ④Configuration File Edit

1.Apache2 Install , Virtual Host Configuration 1.1 Apache2 install 2. Use of CGI Scripts ①CGI availability check 3. PHP installation and configuration 4. Digest authentication with Apache2 Since Basic Authentication, a well-known authentication authorization method for http, sends authentication information in plain text, there is a risk of ID and password leakage if the packet is intercepted. On the other hand, Digest Authentication encrypts and transmits authentication information, so there is almost no risk of information leakage.

clamav(anti-virus) 1.Clam AntiVirus Install # dnf -y install clamav clamd clamav-update 2.Edit Clam AntiVirus configuration file Mail Server Installation 1. Postfix 1.1 Install Install Postfix and build an SMTP server # dnf -y install postfix Mail Server : Postfix + Clamav + clamav-milter+SpamAssassin 1.Real-time scanning of e-mails ①clamav-milter Install Virus checks are performed on the mail server side using Clam AntiVirus. The mail server and Clam AntiVirus are linked using clamav-milter.

1. SSL Certificate Acquisition ( Let's Encrypt ) Install the latest open ssl # dnf install openssl-devel 1.1 advance preparation 1.Package management system Snappy installation Since 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 https Install the following # dnf -y install mod_ssl 2.1 Edit ssl.conf file 3. SSL/TLS (Let's Encrypt) settings on the mail server 3.1 Obtaining a certificate for the mail server Obtain 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.

MySQL8 Install ＃ dnf -y install mysql-server charset.cnf   Create a new one with the f WordPress Install 1. Create database for Word Press As an example, assume database [wp_db] database user [wp_user] password [?W123456]

Suricata SURICATA 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.

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.advance preparation ①Add a CodeReady repository and install the required software

Tripwire 1.Download and installation # cd /usr/local/src # wget https://rpmfind.net/linux/epel/8/Everything/x86_64/Packages/t/tripwire-2.4.3.7-16.el8.x86_64.rpm # rpm -Uvh tripwire-2.4.3.7-16.el8.x86_64.rpm 2.Passphrase setting Set site passphrase and local passphrase Chkrootkit nstall a rootkit detection tool called chkrootkit to check whether a rootkit has been installed on the Linux server. Since chkrootkit is checked using the following command, it is desirable to install it in the early stages after Linux installation, since it is useless after the command itself has been tampered with so that rootkit cannot be detected. [Commands used by chkrootkit] awk, cut, echo, egrep, find, head, id, ls, netstat, ps, strings, sed, uname

1.Website data backup 1-1.Backup under /var/www/html ①Create backup script file # cd /var/www/system # vi backup_html.sh 2.MySQL database backup ①Create backup script file # cd /var/www/system # vi db_my_backup.sh 3.Restore backup files under html ①Store HTML backup files in "/ (root)" directory 4.Restore Mysql backup file ①Save the database backup file to any directory and （In the example, the directory is "/var/www/backup/db_bak".）Extracting data

Suricata SURICATA 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.Apache2 Install , Virtual Host Configuration 1.1 Apache2 install 2. Use of CGI Scripts ①CGI availability check 3. PHP installation and configuration 4. Digest authentication with Apache2 Since Basic Authentication, a well-known authentication authorization method for http, sends authentication information in plain text, there is a risk of ID and password leakage if the packet is intercepted. On the other hand, Digest Authentication encrypts and transmits authentication information, so there is almost no risk of information leakage.

1.FTP Server 1.1vsftpd Install # dnf -y install vsftpd 1.2vsftpd configuration Save the unedited vsftpd.conf with .bak # cp /etc/vsftpd/vsftpd.conf /home/huong/vsftpd.conf.bak 2. vsftpd SSL/TLS Configure Vsftpd to use SSL/TLS 2.1 Create self-signed certificates This work is not required if you are using a trusted, legitimate certificate such as Let's Encryp 3. File server installation with Samba Build a file server with access rights that requires user authentication with Samba. Installation Procedure ①Create shared folders with access rights that require user authentication ②Accessible group creation ③Creation of users belonging to accessible groups ④Configuration File Edit

SSH connection with authentication using public key  Creation of public and private key pairs Create 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.