Vietnam Cloud Server Rental Security Reinforcement List Includes Firewall And Access Control Solutions

1.

preparedness and risk assessment

step 1: sort out assets and services (list public ip addresses, open ports, and running applications).
step 2: assess threats (ssh brute force, web vulnerabilities, unpatched, etc.).
step 3: develop maintenance windows and rollback plans, and prepare snapshots/backups in case changes go wrong.

2.

basic system update and account management

step 1: upgrade the system package (debian/ubuntu: apt update && apt upgrade -y; centos: yum update -y).
step 2: create a normal administrative user and disable root. log in directly: adduser adminuser && usermod -ag sudo adminuser.
step 3: set a strong password policy or use pam to strengthen it, and delete useless users and accounts (check /etc/passwd).

3.

ssh hardening and key management

step 1: generate a key (run locally: ssh-keygen -t ed25519 -c "your@me") and append the public key to the server ~/.ssh/authorized_keys.
step 2: modify /etc/ssh/sshd_config. it is recommended to change: permitrootlogin no, passwordauthentication no, pubkeyauthentication yes, port 22 (can be changed to a non-standard port). after saving, systemctl restart sshd.
step 3: set ssh key permissions: chmod 700 ~/.ssh && chmod 600 ~/.ssh/authorized_keys.

4.

cloud security group and host firewall practical operation

step 1 (cloud console): create a security group in the vietnam cloud provider console, whitelist rules, open only necessary ports (such as tcp 22/443/80), and limit the management ip range.
step 2 (ufw example, ubuntu): apt install ufw -y; ufw default deny incoming; ufw default allow outgoing; ufw allow from 203.0.113.4 to any port 22 proto tcp; ufw allow 443/tcp; ufw enable.
step three (iptables example): iptables -f; iptables -a input -m conntrack --ctstate established,related -j accept; iptables -a input -p tcp --dport 22 -s 203.0.113.4 -j accept; iptables -a input -p tcp --dport 443 -j accept; iptables -a input -j drop; save the rules (iptables-save > /etc/iptables.rules) and write the systemd recovery script.

5.

intrusion prevention (fail2ban) and login restrictions

step 1: install fail2ban (ubuntu/debian: apt install fail2ban -y; centos: yum install epel-release && yum install fail2ban -y).
step 2: create /etc/fail2ban/jail.local, example content: [sshd] enabled = true port = 22 filter = sshd maxretry = 5 bantime = 3600 findtime = 600.
step 3: systemctl enable --now fail2ban; use fail2ban-client status sshd to view the ban record and add it to the whitelist if necessary (ignoreip = 203.0.113.4/32).

6.

bastion hosts, vpns and the principle of least access

step 1 (bastion host): deploy a bastion host in a separate management subnet (only open ssh to the management ip), and all operations and maintenance go through the bastion host springboard.
step 2 (wireguard quick example): apt install wireguard -y; wg genkey | tee /etc/wireguard/privatekey | wg pubkey > /etc/wireguard/publickey; edit /etc/wireguard/wg0.conf to configure server/client, and start systemctl enable --now wg-quick@wg0.
step 3: in production environments, it is recommended to use vpn or bastion host to connect to intranet services to avoid directly exposing the management port to the public network.

7.

log auditing, monitoring and automated patching

step 1: enable system logs and remote centralized logs (rsyslog/graylog/elk), and push /var/log to the centralized log server.
step 2: install auditd to monitor sensitive operations and configure rules (auditctl -w /etc/ssh/sshd_config -p wa -k ssh_cfg_change).
step 3: enable automatic security updates (ubuntu: apt install unattended-upgrades && dpkg-reconfigure --priority=low unattended-upgrades) and make regular snapshot backups.

8.

q: which is more important, cloud security group or host firewall?

answer: both are important. the cloud security group is the first line of boundary protection and should be strictly whitelisted in the console; the host firewall (ufw/iptables), as the second line of defense, should be restricted to a more fine-grained level (interfaces, processes), and is more secure when used together.

9.

q: how to temporarily allow access from dynamic ip?

answer: temporary solution: modify the security group temporarily in the cloud console and record the changes; a safer approach is to use a vpn or bastion host and issue short-term wireguard/otp accounts to temporary users, or add a temporary whitelist in fail2ban.

10.

q: what are the daily operations and best practices after deployment?

answer: keep the system automatically updated and patched, regularly rotate ssh keys and api keys, enable multi-factor authentication, configure alarms (login failure, abnormal traffic), regularly practice the recovery process, and maintain the principle of least privilege.