Modify /etc/ssh/sshd_config
:
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| # Disable root login
PermitRootLogin no
# Change the default port
Port 12345
# Enable login with key
RSAAuthentication yes
PubkeyAuthentication yes
# Disable login with password
UsePAM no
PasswordAuthentication no
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After that, remember to restart sshd: sudo /etc/init.d/ssh restart
(for Debian/Ubuntu) or sudo service sshd restart
(for CentOS).
Create the file /etc/iptables.test.rules
, and enter rules:
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| *filter
# Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT
# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allows all outbound traffic
# You could modify this to only allow certain traffic
-A OUTPUT -j ACCEPT
# Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT
# Allows SSH connections
# The --dport number is the same as in /etc/ssh/sshd_config
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT
# Now you should read up on iptables rules and consider whether ssh access
# for everyone is really desired. Most likely you will only allow access from certain IPs.
# Allow ping
# note that blocking other types of icmp packets is considered a bad idea by some
# remove -m icmp --icmp-type 8 from this line to allow all kinds of icmp:
# <https://security.stackexchange.com/questions/22711>
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
# log iptables denied calls (access via 'dmesg' command)
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7
# Reject all other inbound - default deny unless explicitly allowed policy:
-A INPUT -j REJECT
-A FORWARD -j REJECT
COMMIT
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Apply these rules:
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| sudo iptables-restore < /etc/iptables.test.rules
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And see the difference:
Save the rules:
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| iptables-save > /etc/iptables.up.rules
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Create file /etc/network/if-pre-up.d/iptables
, and add these lines to it:
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| #!/bin/sh
/sbin/iptables-restore < /etc/iptables.up.rules
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Add executable permision for the file:
chmod +x /etc/network/if-pre-up.d/iptables
To check who is listening on TCP port 12345:
lsof -n -i4TCP:12345 | grep LISTEN
Modify the file nginx.conf:
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| http {
# Hide nginx version information
server_tokens off;
# Catch all requests with wrong host and return 444 status
server {
listen 80 default_server;
listen [::]:80 default_server;
listen 443 ssl default_server;
listen [::]:443 ssl default_server;
return 444;
}
}
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