Prevent any backends for CentOS

fail2ban

SSH keys

don't use root

there's loads more but can't remember them off the top of my head (on mobile right now).

 

25 Hardening Security Tips for Linux Servers
[Guide] Securing a Linux server
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A few more options are change the SSH port, Whitelist your IP, Block china, etc, etc.

 

Block those China brute forcers!

 

you should install swatch to monitor all unauthorised login attempts and automatically block those IP, which had, say, three failed attempt. Also, you might want to consider blocking certain country address. I have something like this in my test server:

Spoiler: blocking/accepting certain countries.

Code (Text):

# DROP_COUNTRY_MAKE

DROP_COUNTRY_MAKE(){
    for addr in `cat /tmp/cidr.txt|grep ^$1|awk '{print $2}'`
    do
        echo "-A DROP_COUNTRY -s $addr -m limit --limit 1/s -j LOG --log-prefix\
\"[IPTABLES DENY_COUNTRY] : \"" >> $IPTABLES_CONFIG
        echo "-A DROP_COUNTRY -s $addr -j DROP" >> $IPTABLES_CONFIG
    done
    grep ^$1 $IP_LIST >> $CHK_IP_LIST
}

# obtain IP address list.
IP_LIST=/tmp/cidr.txt
CHK_IP_LIST=/tmp/IPLIST
if [ ! -f $IP_LIST ]; then
    wget -q http://nami.jp/ipv4bycc/cidr.txt.gz
    gunzip -c cidr.txt.gz > $IP_LIST
    rm -f cidr.txt.gz
fi
rm -f $CHK_IP_LIST

# accept access from Japan and Australia
ACCEPT_COUNTRY_MAKE JP
ACCEPT_COUNTRY_MAKE AU

# Top 5 sources of attack to Japanese police facility.
# http://www.cyberpolice.go.jp/detect/observation.html
DROP_COUNTRY_MAKE CN
DROP_COUNTRY_MAKE CA
DROP_COUNTRY_MAKE IR
DROP_COUNTRY_MAKE NL
DROP_COUNTRY_MAKE TW
echo "-A INPUT -j DROP_COUNTRY" >> $IPTABLES_CONFIG

 

Look in this helpful script https://github.com/marshyski/quick-secure/blob/master/quick-secure

 

If you are using SSH keys, there's no need for fail2ban, change SSH port or block some countries.

 

China likes to brute force..dedi's. Also like no china people are actual minecraft players. So block them, same with Russia and North Korea. They will likely brute force.

 

Disable root logins, have a username that is sort of random i.e jki789123. As well as that having a strong password with a variation of special characters and lower case and upper case as well as numbers is a good idea. If you really want to you could also change the ssh port, also don't keep any ports open that you don't need open.

 

SSH keys are much more secure than even random passwords.

 

Why would anyone who has internet in North Korea brute force you?

 

Not anyone, but they don't even speak English. First of all they won't help your server, second of all North Korea hackers like to brute force.