Configuration record of ubuntu simple firewall ufw

I am operating under root, ordinary users need sudo permission
ufw disable to close
ufw enable Open
this file to close ipv6
/etc/default/ufw
View rules
ufw status
Add rules example:

            ufw default allow outgoing
            ufw default deny incoming       
            ufw default deny   关闭所有外部访问端口
            ufw allow ssh       ufw allow 22
            ufw allow 80/tcp 
            ufw allow http/tcp
            ufw allow 1725/udp
            ufw allow 25:29/udp
            ufw allow from 123.45.67.89
            ufw allow from 123.45.67.89/24
            ufw allow from 123.45.67.89 to any port 22 proto tcp
             sudo ufw allow from 192.168.1.1 允许此IP访问所有的本机端口
             sudo ufw deny proto tcp from 10.0.0.0/8 to 192.168.0.1 port 22 要拒绝所有的TCP流量从10.0.0.0/8 到192.168.0.1地址的22端口

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Log directory: vim /var/log/ufw .log
sudo ufw logging on enable log
sudo ufw logging off disable log
sudo ufw logging low|medium|high

1. Sep 16 15:08:14 <hostname> kernel: [UFW BLOCK] IN=eth0 OUT= MAC=00:00:00:00:00:00:00:00:00:00:00:00:00:00 SRC=0.0.0.0 DST=0.0.0.0 LEN=40 TOS=0x00 PREC=0x00 TTL=249 ID=8475 PROTO=TCP SPT=485 DPT=22 WINDOW=1024 RES=0x00 SYN URGP=0
   The previous values ​​listed The date, time, and hostname of your server. The remaining important information includes:
   • [UFW BLOCK]: This is where the description of the recorded event begins. In this case, it means that the connection is blocked.
   • IN: If it contains a value, then the event is an incoming event
   • OUT: If it contains a value, then the event is an outgoing event
   • MAC: Combination of destination and source MAC addresses
   • SRC: IP of the packet source
   • DST: IP of packet destination
   • LEN: packet length
   • TTL: Packet TTL, or time to live. It will hop between routers until it expires before finding its destination.
   • PROTO: The protocol of the packet
   • SPT: The source port of the packet
   • DPT: destination port of the packet
   • WINDOW: The size of the packet that the sender can receive
   • SYN URGP: Indicates whether a three-way handshake is required. 0 means not required.

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The following three items can check the operating system port monitoring

netstat -an | grep LISTEN | grep -v ^unix”
netstat -ntulp
lsof -i -n -P