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1. SSH Service Security SettingsThe SSH service allows the root user to log in by default, and since the root user already knows the user name and can log in to the server with administrative privileges once the password is known, we will deny this setting.1.1 Creating a General Userf you have created a general user when installing Debian, this procedure is not necessary.If the only user created on the server is root, remote login via SSH will not be possible, so if a user has not been created during OS installation, a user must be created in advance.Users can be created with the "useradd" command. The "-m" option creates a home directory and the "-p" option specifies the password.For example, to set "debianuser" as the user account name and "123456" as the password, execute the following2. Firewall SettingsSince Debian often uses software called "ufw" to configure firewalls, we will configure firewall settings using ufw.Since ufw is not installed when the OS is installed, the ufw package must be installed prior to configuration. The following is a procedure to configure minimal filter settings after installation.Filter rules to be set in ufw• All packets forwarded to the server are rejected• All packets sent from the server to the outside are allowed• The first port to allow is the port for SSH• Limit packets coming into the server

Create a key pairCreate a public/private key pair for a user connecting to a Linux server using OpenSSH.Use ssh-keygen to create the key pair.The creation of a public/private key pair must be done as a user with remote login 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.

Web server Apache2 installationAllow http:80 and https:443 ports in UFW before installation3.  Apache2; Using Perl ScriptsEnable CGI to make Perl scripts available①Install Perl4 Apache2 : Using PHP Scripts①Install PHP5. Virtual Host SettingsCopy the default configuration file (file name is arbitrary, in this case vhost-yourdomain.conf as an example) and configure the virtual host6. Digest authentication with Apache2Since 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.Antivirus software Clamav installedInstall Clam AntiVirus, a free anti-virus software for Linux, as an anti-virus measure.By installing this anti-virus software, you can not only scan the entire server for viruses, but also scan incoming and outgoing mail for viruses if you build and configure a mail server.2. Mail server installationPostfix was developed as a Mail Transport Agent (MTA) to replace sendmail, and is a mail server that is highly compatible with sendmail, secure, easy to maintain, and fast.In addition, since Postfix only functions as an SMTP server for sending mail, the POP server Dovecot for receiving mail will be installed separately in the latter half.3 Applied ClamAV to mail server PostfixSet up Postfix and Clamav to work together to scan incoming and outgoing mail in real time.4 Apply spam checks to the mail server4.1 Spam checking using spamassassin and procmail①spamassassin and procmail installation

1. Obtain a certificate(Let's Encrypt)1.1 advance preparation1.Enable mod_ssl# a2enmod ssl2.Package management system Snappy installedLet's Encrypt's SSL certificate issuing tool "certbot" is recommended to be installed using "snap" after 2021, so install Snapd first.2. SSL/TLS (Let's Encrypt) configuration for Apache2①Edit Apache2 SSL-related configuration fileshoge.com-ssl in hoge.com-ssl.conf is an arbitrary name3. 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.

1. MariaDB1.1 Install# apt install mariadb-serverMariaDB version confirmation# mariadb -Vmariadb Ver 15.1 Distrib 10.11.6-MariaDB, for debian-linux-gnu (x86_64) using EditLine wrapper1.2 MariaDB Server Security SettingsMariaDB comes with a default security script, mariadb-secure-installation, which can be used to improve the security of your MariaDB installation, includingSet a password for the root account (if necessary).Disable remote root login to the database.Delete anonymous user accounts.Delete the test database to which anonymous users have access by default.2.WordPress2.1 Database CreationCreate a database for Word Press (for example, in this case, the database name is "wp_db", the user name is "wp_user", and the password is "?Y123456y")

Debian12.8 ; Suricata + Elastic Stack + KibanaPrerequisite.We will install Suricata IDS and ElasticStack on the following servers・1st server Suricata IDS & Filebeat : Debian12.5 IP address (192.168.11.83)・2nd server　ElasticStack & kibana　: Ubunru22.04 IP address(192.168.11.100) 1st server Suricata InstallSURICATA IDS/IPS is an open source IDS that monitors communications on the network and detects suspicious traffic. Its 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.

LogwatchLogwatch compiles various logs together and delivers them as a report via email on a regular daily basis. This is a useful tool for detecting unauthorized access and problems and monitoring servers.Chkrootkitchkrootkit is a tool to detect the presence of rootkits.Note that chkrootkit is meaningless after it has already been tampered with, so consideration must be given when introducing it. In addition, chkrootkit has no function to automatically deal with a rootkit even if it detects it, so it must be dealt with manually after detection.