Firewall

ssh

ecsumcs.eastus.cloudapp.azure.com
sudo vim /etc/ssh/sshd_config
Add allowed users to the bottom
- AllowUsers lchen jzhang fzhou jliao
sudo service ssh restart, retart ssh service, 05.29.2019
remove the access from ssh secure shell, 05.29.2019

Monitor network

iftop, monitor the network activities

Check all input and output activities

netstat -tuapn, monitor the connected network activities

Check the activities of accessing the current server

iptables, add suspicious ips into the blocked list

iptables

Download ips of US

#!/bin/bash

# allow the US ips
for ip in `more us.zone`
do
        echo $ip
        iptables -A INPUT -s $ip -j ACCEPT
        iptables -A OUTPUT -s $ip -j ACCEPT
done

# block the ips from other countries
iptables -A INPUT -j DROP
iptables -A OUTPUT -j DROP

Reference

Algorithm Negotiation failed when trying to connect to server