How to check DOS/DDOS attack in the server

These are few steps to be taken when you feel that the server is under DOS/DDOS attack:

Step 1: Check the load in the server using the command "w" or "uptime".

Step 2: Check which process is utilizing maximum CPU by "top -cd3" & press SHIFT +M. This will show you the memory usage in decreasing order.

Step 3: Check which IP address is taking maximum connection using the command:

netstat -alpn | grep :80 | awk '{print $5}' |awk -F: '{print $(NF-1)}' |sort | uniq -c | sort -n

Step 4: Check the IP address of the server having maximum connection using the command:

netstat -alpn | grep :80 | awk '{print $4}' |awk -F: '{print $(NF-1)}' |sort | uniq -c | sort -n

Step 5: Then block the IP address using APF firewall "apf -d <IP address>" or using CSF firewall "csf -d <IP address>

Thank you.

Comments

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