Direct Answer: Production Ubuntu server hardening involves disabling root SSH login, enforcing Ed25519 public key authentication, deploying UFW firewall with strict default-deny policies, configuring Fail2ban for brute-force mitigation, removing unnecessary network services, and automating security updates with unattended-upgrades.
Public-facing SSH daemons on default port 22 are bombarded with thousands of automated dictionary attacks daily. By locking down /etc/ssh/sshd_config, you neutralize automated scans before they consume CPU and network sockets.
# /etc/ssh/sshd_config hardened parameters
Port 2222
Protocol 2
PermitRootLogin no
PasswordAuthentication no
PermitEmptyPasswords no
PubkeyAuthentication yes
AuthenticationMethods publickey
X11Forwarding no
MaxAuthTries 3
MaxSessions 4
ClientAliveInterval 300
ClientAliveCountMax 2
AllowGroups sudo sysadmin
Implement an aggressive default-deny posture. Only explicitly whitelisted ingress ports should be opened:
# Configure UFW default policies
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow 2222/tcp comment "Hardened SSH Port"
sudo ufw allow 80/tcp comment "Nginx HTTP"
sudo ufw allow 443/tcp comment "Nginx HTTPS"
sudo ufw enable
# Configure Fail2ban jail for SSH in /etc/fail2ban/jail.local
[sshd]
enabled = true
port = 2222
filter = sshd
logpath = /var/log/auth.log
maxretry = 3
findtime = 600
bantime = 86400
action = iptables-multiport[name=SSH, port="2222", protocol=tcp]
| Security Vector | Default Ubuntu Setting | Hardened Enterprise Standard |
|---|---|---|
| Root Login | Permitted with password | Disabled; Sudo with individual user logs |
| SSH Keys | Optional | Enforced Ed25519 (256-bit elliptic curve) |
| Firewall | Inactive / Allow All | UFW Default-Deny Incoming |
| Kernel Shared Memory | Writable / Executable | Hardened via /etc/fstab (nodev, nosuid, noexec) |
| Security Patches | Manual apt update |
Automated daily unattended-upgrades |
Protect against SYN flood attacks, IP spoofing, and packet redirection by appending these parameters to /etc/sysctl.d/99-security.conf:
net.ipv4.tcp_syncookies = 1
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.all.rp_filter = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1
fs.protected_hardlinks = 1
fs.protected_symlinks = 1
Ed25519 provides superior security with significantly smaller key sizes (68 characters vs thousands in RSA), faster cryptographic signature verification, and mathematical immunity to side-channel timing attacks.
By default, no. Security patches for libraries and services are applied seamlessly. For kernel updates requiring a reboot, configure maintenance window reboots at 03:00 AM on Sunday, or utilize livepatch services.
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