Q. How do I find out if I Linux box is under DoS attack or not form a shell prompt?
A. You can simply use netstat command to print out a list of all open connection to your Linux box. The list will be sorted out using sort command including total number of connections from a specific IP address.
Task: Looking at open connections (DoS)
Login as the root user
Type the following command
# netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n