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6

I feel like this should be a really simple thing to do, but googling and checking SF I didn't see anything. I'm trying to make my Fedora server not respond to ping, how do I do that?

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6  
I've never understood the advantages of disabling ICMP Echo Requests on servers. It makes monitoring and debugging network connectivity troublesome. Servers will usually have one or more low ports open for service anyway, so it's not like you can blackhole them. Could you let me know your reason, please? – Martijn Heemels Sep 4 '09 at 13:21
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It's done only for a false sense of security. – Michael Hampton Mar 6 at 10:15

9 Answers

up vote 16 down vote accepted

To disable the PING response, add the following line to your init script for the network:

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

To reenable the PING response do this:

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

UPDATE:

To make the change PERMANENT add the following line to /etc/sysctl.conf:

net.ipv4.icmp_echo_ignore_all=1

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up vote 10 down vote

Add the following line to /etc/sysctl.conf:

net.ipv4.icmp_echo_ignore_all=1

It has the same effect as the above echo lines.

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up vote 9 down vote

It is better to use firewall for these purposes, so that you can optionally enable ping from some systems, esp monitoring systems

iptables -t filter -I INPUT -p icmp --icmp-type echo-request -s monitoring_system -j ACCEPT
iptables -t filter -I INPUT -p icmp --icmp-type echo-request -j DROP
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4  
+1 For selective enabling – Josh Brower Jul 29 '09 at 23:30
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Just in case it's not obvious to iptables newbies, replace "monitoring_system" with the IP/range of the server(s) which should be able to ping the server. All other ping requests will be silenty dropped. – Coops Jul 30 '09 at 8:40
up vote 0 down vote

This article explains how to do this.

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up vote 0 down vote

Just do this:

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all
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up vote 0 down vote

Firewall block ICMP connections.

especially icmp echo.

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6  
However, do not block all ICMP traffic because this will e.g. break Path MTU discovery. – knweiss Jul 28 '09 at 22:08
Path MTU Blackholes are no fun at all. – Mark Johnson Sep 3 '09 at 15:27
up vote 0 down vote

Additionally, you can use "Blackhole" security: the server simply won't answer connection attemps to closed ports, so portscan becomes a difficult one ;)

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up vote 0 down vote

open your /etc/sysctl.conf and append this line

net.ipv4.icmp_echo_ignore_all = 1

and execute this command

sysctl -p

it's still usable after reboot

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up vote 0 down vote

You can also use this command to disable ping request

sysctl net.ipv4.icmp_echo_ignore_all=0

To enable it again 

sysctl net.ipv4.icmp_echo_ignore_all=1

Finally save it sysctl -p

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