Allow/deny,disable or drop/block ping packets on Linux serves

Allow/deny,disable or drop/block ping request
Ping is a computer network administration software utility used to test the reachability of a host on an Internet Protocol (IP) network, and to measure the round-trip time for messages sent from the originating host to a destination computer and echoed back to the source. 

The name comes from active sonar terminology that sends a pulse of sound and listens for the echo to detect objects under water,although it is sometimes interpreted as a backronym to packet Internet groper
Blocking PING on server is helpful sometimes, if the server is continue to face any type of DDoS attack by using the PING feature. By using iptables we can simply stop the PING option.
STEP : 1
You can setup kernel variable to drop all ping packets. Type the following command at shell prompt:
This instructs the kernel to simply ignore all ping requests.

echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all

To enable ping request type the command:

echo "0" > /proc/sys/net/ipv4/icmp_echo_ignore_all

You can add following line to /etc/sysctl.conf file:

# vi /etc/sysctl.conf 

Append following line:

net.ipv4.icmp_echo_ignore_all = 1

Save and close the file.
STEP : 2
Also we can manage it by the help of 'iptables'. The 'ping' is using ICMP to communicate. We can simply manage the 'icmp : Internet Controlled Message Protocol'from iptables.
The below pasted switches are required for creating a rule for managing icmp.

-A : Add a rule
-D : Delete rule from table
-p : To specify protocol (here 'icmp')
--icmp-type : For specifying type
-J : Jump to target

Normally using icmp types and its Codes Click here for ICMP Types and Codes

echo-request   :  8
echo-reply     :  0

How to block PING to your server with an error message?

In this way you can partially block the PING with an error message 'Destination Port Unreachable'. Add the following iptables rules to block the PING with an error message. (Use REJECT as Jump to target)

iptables -A INPUT -p icmp --icmp-type echo-request -j REJECT

Result : - 

[root@redhat ~]# ping hackthesec.co.in
Pinging hackthesec.co.in [216.239.34.21] with 32 bytes of data:
From 216.239.34.2 icmp_seq=1 Destination Port Unreachable
From 216.239.34.2 icmp_seq=2 Destination Port Unreachable
From 216.239.34.2 icmp_seq=3 Destination Port Unreachable

To block without any messages use DROP as Jump to target.

iptables -A INPUT -p icmp --icmp-type echo-request -j DROP
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j DROP

Allow Ping from Outside to Inside

iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT

How to block PING from your server?
In this way you can block PING option from your server to outside. Add these rules to your iptables to do the same.

Block PING operation with message 'Operation not permitted'

iptables -A OUTPUT -p icmp --icmp-type echo-request -j DROP

Result:-

root@test [~]# ping google.com
PING google.com (173.194.34.136) 56(84) bytes of data.
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted
ping: sendmsg: Operation not permitted

To block with out any error messages
For this, DROP the echo-reply to the INPUT chain of your iptables.

iptables -A OUTPUT -p icmp --icmp-type echo-request -j DROP
iptables -A INPUT -p icmp --icmp-type echo-reply -j DROP

Allow Ping from Inside to Outside

iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT
iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT

You can use the icmp code instead of icmp-type name for adding rule to iptables.

www.hackthesec.co.in