Difference between revisions of "How to block someone's IP"

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To block incoming IP, use this command:
To block incoming IP, use this command:


    iptables -A INPUT -s IP -j DROP
iptables -A INPUT -s IP -j DROP


For example:
For example:


    iptables -A INPUT -s 123.123.123.123 -j DROP
iptables -A INPUT -s 123.123.123.123 -j DROP


To save the rules (On Centos), run:
To save the rules (On Centos), run:
 
  /etc/init.d/iptables save
/etc/init.d/iptables save


Question: I want allow only specified IPs to my server and dissallow any other connections, how I could do that?
Question: I want allow only specified IPs to my server and dissallow any other connections, how I could do that?
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First of all enter all friendly ips:
First of all enter all friendly ips:


  iptables -A INPUT -s friendlyip. -j ACCEPT
iptables -A INPUT -s friendlyip. -j ACCEPT
  iptables -A INPUT -s another.friendly.ip -j ACCEPT
iptables -A INPUT -s another.friendly.ip -j ACCEPT
  iptables -A INPUT -s 127.0.0.1 -j ACCEPT # yes, accept connections from localhost.
iptables -A INPUT -s 127.0.0.1 -j ACCEPT # yes, accept connections from localhost.


And the most end enter:
And the most end enter:


  iptables -A INPUT -s 0/0 -j DROP
iptables -A INPUT -s 0/0 -j DROP


Thats it.
Thats it.

Revision as of 14:14, 24 January 2014

First of all install iptables if needed:

yum -y install iptables


To block incoming IP, use this command:

iptables -A INPUT -s IP -j DROP

For example:

iptables -A INPUT -s 123.123.123.123 -j DROP

To save the rules (On Centos), run:

/etc/init.d/iptables save

Question: I want allow only specified IPs to my server and dissallow any other connections, how I could do that?

First of all enter all friendly ips:

iptables -A INPUT -s friendlyip. -j ACCEPT
iptables -A INPUT -s another.friendly.ip -j ACCEPT
iptables -A INPUT -s 127.0.0.1 -j ACCEPT # yes, accept connections from localhost.

And the most end enter:

iptables -A INPUT -s 0/0 -j DROP

Thats it.

If in future you will want to add some more ips, just first reject rule with DROP, and some friendly ip and then apply DROP rule again.

Very important: Don't forget to add ISP/router to your friendly ip address list!!!

How to unblock IP

Search for the IP under /etc/sysconfig/iptables:

grep 123.123.123.123 /etc/sysconfig/iptables

This would give the following output:

-A INPUT -s 123.123.123.123 -j DROP
-A INPUT -s 123.123.123.123 -j ACCEPT

Then you can delete the rule using the '-D' option in iptables:

iptables -D INPUT -s 123.123.123.123 -j DROP

Now IP 123.123.123.123 is unblocked.