Block range of IP Addresses

Solution 1:

To block 116.10.191.* addresses:

$ sudo iptables -A INPUT -s 116.10.191.0/24 -j DROP

To block 116.10.*.* addresses:

$ sudo iptables -A INPUT -s 116.10.0.0/16 -j DROP

To block 116.*.*.* addresses:

$ sudo iptables -A INPUT -s 116.0.0.0/8 -j DROP

But be careful what you block using this method. You don't want to prevent legitmate traffic from reaching the host.

edit: as pointed out, iptables evaluates rules in sequential order. Rules higher in the ruleset are applied before rules lower in the ruleset. So if there's a rule higher in your ruleset that allows said traffic, then appending (iptables -A) the DROP rule will not produce the intended blocking result. In this case, insert (iptables -I) the rule either:

• as the first rule

sudo iptables -I ...

• or before the allow rule

sudo iptables --line-numbers -vnL

say that shows rule number 3 allows ssh traffic and you want to block ssh for an ip range. -I takes an argument of an integer that's the location in your ruleset you want the new rule to be inserted

iptables -I 2 ...

Solution 2:

sudo /sbin/iptables -A INPUT -s 116.10.191.0/24 -j DROP

This blocks the range. You can expand the subnet as needed with the same general format.

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Solution 3:

As an alternative approach you could use something as simple as fail2ban. It institutes a timeout for successive failed login attempts and makes bruteforcing infeasible since they only get a few chances per timeout. I set my time out length to 30 minutes. By the time they're an hour or two in, they realize they won't be able to make any headway and give up.