Guides tagged “firewall”
Step-by-step MdmHost guides about firewall, sorted A-Z.
76 guides · page 3 of 4
Linux Firewall: Using nftables to Drop Malformed Packets and Attack Vectors
Build nftables chains that drop malformed packets, invalid conntrack states and common scan patterns before they reach your services, then verify the counters.
Linux Firewall: Using UFW to Block Specific Source IP Ranges Automatically
Block a source IP range in UFW with one command, then keep a blocklist file and a cron job that re-applies it so new ranges are dropped without manual work.
Lock down SSH on a Linux VPS: a complete checklist
A step-by-step SSH hardening checklist for Linux VPS and WHM servers: keys only, no root password login, firewall limits by IP, brute-force bans and safe testing.
Locked out by your firewall? How to get back into your VPS
If a firewall rule blocked SSH, you can still reach your server through the browser console in your VPS provider's control panel. Disable the firewall, fix the rule and turn it back on safely.
Make iptables rules survive a reboot
iptables rules live in memory and disappear on reboot. Save them with netfilter-persistent on Debian and Ubuntu or iptables-services on AlmaLinux and Rocky Linux.
Manage Windows Defender Firewall on Windows Server with PowerShell
Create, list, restrict and remove Windows Defender Firewall rules on a Windows VPS using the GUI and PowerShell, including limiting RDP to your IP and logging drops.
Migrate iptables rules to nftables
Move an existing iptables firewall to native nftables. Check whether you run iptables-nft or legacy, export with iptables-save, translate the rules, test them and switch the boot service.
Open and close ports in CSF (TCP_IN, TCP_OUT, UDP_IN, UDP_OUT)
Edit the CSF port lists to open a port for a new service, close ports you do not use, and restrict a port such as SSH to trusted IPs on a cPanel/WHM server.
Open ports with UFW: single ports, ranges and trusted IPs
Open TCP and UDP ports in UFW, allow port ranges, limit access to one IP or subnet, label rules with comments and confirm everything with ufw status numbered.
Port forwarding and masquerading with firewalld
Forward a port to another local port or to a different host with firewalld, enable masquerading so replies find their way back, then test and make the rules permanent.
Port forwarding and NAT with UFW before.rules
Forward a public port on your VPS to a backend server or VPN client with UFW. Turn on IP forwarding, add a nat table to before.rules, allow routed traffic and test from outside.
Port open in the firewall but still unreachable: how to fix it
You allowed a port in the firewall but connections still fail. Work through each layer, from the listening address to the server and client networks, to find the real block.
Ports, protocols and TCP vs UDP explained
How ports and protocols let one server run many services, the real difference between TCP and UDP, and which one common services use.
Protect SSH from brute-force attacks with Fail2ban
Install Fail2ban, create a safe jail.local for SSH, check which addresses are banned and unban yourself if you mistype a password too often.
Protect your website with Cloudflare WAF custom rules
Use Cloudflare WAF custom rules to block bad countries, bots and attack paths, challenge visitors to wp-login.php, and allow your own IP, before traffic reaches your hosting.
Put Remote Desktop behind a WireGuard VPN
Install WireGuard on your Windows server, connect your own computer as a client, then limit the RDP port 3389 rule to the VPN subnet so only VPN users can reach the login screen.
Rate-limit SSH and other ports with ufw limit
Use ufw limit to slow down SSH brute-force attempts. Learn how the 6-connections-in-30-seconds rule works, apply it to a custom SSH port, pair it with Fail2ban and test it.
RDP over UDP vs TCP: check and choose the transport
Remote Desktop can carry your session over TCP, UDP or both. Learn how each is used, how to see which one your session runs on, and how to force TCP when UDP misbehaves.
Read and tune UFW firewall logs
Turn on UFW logging at the right level, find [UFW BLOCK] lines in the journal or ufw.log, read the SRC, DPT and PROTO fields and keep log volume under control.
Read the Imunify360 Incidents log to understand attacks (root guide)
Use the Imunify360 Incidents tab and CLI as root to see brute-force attempts, WAF hits and blocked IPs, spot patterns, and decide when to whitelist, block or tune rules.
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