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UFW – IPtables Firewall configuration made easier

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    UFW (Uncomplicated Firewall) is the easiest way to make your server secure by blocking all incoming connections on ports you do not want to use.

    So at first, install ufw :

    apt install ufw -y
    ## Check the status of ufw with 
    ufw status
    
    ## to identify what services are running on your server use 
    netstat -tulpn
    
    ##  enable logging 
    ufw logging on
    
    ##  Use the default rules to allow outgoing traffic and to deny all incoming traffic. 
    ufw default allow outgoing
    ufw default deny incoming
    
    ## allow SSH - DNS - HTTP and HTTPS  - NTP
    ufw allow 22
    ufw allow 53
    ufw allow http
    ufw allow https
    ufw allow 123
    
    ## Librenms SNMP and Unix-agent
    ufw allow 161
    ufw allow 6556
    
    ## Netdata dashboard 
    ufw allow 19999
    
    ## Rsync
    ufw allow 873
    
    ## EasyEngine default backend
    ufw allow 22222
    
    ### Some other examples :
    
    ## Allow connections on all ports from an IP 
    ufw allow from 123.45.67.89
    
    ## Allow connections on all ports from a subnet
    ufw allow from 123.45.67.89/24
    
    ## Specify a port + an IP + a protocol 
    ufw allow from 123.45.67.89 to any port 22 proto tcp
    
    # Whitelist Cloudflare network IPv4+IPv6
    wget https://raw.githubusercontent.com/Paul-Reed/cloudflare-ufw/master/cloudflare-ufw.sh
    bash cloudflare-ufw.sh

    When you have set all the rules you need, enable ufw with :

    ufw enable

    Check sometimes the server syslog to see if there is some missing rules in your configuration :

    tail -f /var/log/syslog

    You should see some connections blocked by UFW :

    Jun XX 18:28:X server kernel: [ 8544.753005] [UFW BLOCK] IN=eth0 OUT= MAC=00:50:56:xx:xx:xx:00:ff:ff:ff:ff:xx:xx:00 SRC=xx.xx.173.85 DST=xx.xx.51.219 LEN=40 TOS=0x00 PREC=0x00 TTL=246 ID=28251 PROTO=TCP SPT=59043 DPT=21021 WINDOW=1024 RES=0x00 SYN URGP=0

    SRC: IP source
    DST: Destination IP
    SPT: Port source
    DPT: Destination Port

    in Security