Linux: Iptables Examples For New SysAdmins Part -->3

Before see this post please read my previous post (Linux: Iptables Examples For New SysAdmins Part -->2)

#12: Log and Drop Packets

 

Type the following to log and block IP spoofing on public interface called eth1

# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j LOG --log-prefix "IP_SPOOF A:

# iptables -A INPUT -i eth1 -s 10.0.0.0/8 -j DROP

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Linux: Iptables Examples For New SysAdmins Part -->2

Before see this post please read my previous post (Linux: Iptables Examples For New SysAdmins Part -->1)

#3: Delete Firewall Rules

To display line number along with other information for existing rules, enter:

# iptables -L INPUT  -n --line-numbers
# iptables -L OUTPUT -n --line-numbers
# iptables -L OUTPUT -n --line-numbers | less
# iptables -L OUTPUT -n --line-numbers | grep 192.0.43.10

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Linux: Iptables Examples For New SysAdmins Part -->1

Linux comes with a host based firewall called Netfilter. According to the official project site:

netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.

This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. I strongly recommend that you first read our quick tutorial thatexplains how to configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux. This post list most common iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders.

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Redhat / CentOS Iptables Firewall Configuration

H

ow do I configure a host-based firewall called Netfilter (iptables) under CentOS / RHEL / Fedora / Redhat Enterprise Linux?

Icon reference for Firewall

Netfilter is a host-based firewall for Linux operating systems. It is included as part of the Linux distribution and it is activated by default. This firewall is controlled by the program called iptables. Netfilter filtering take place at the kernel level, before a program can even process the data from the network packet.

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CentOS / RHEL: Disable or Enable SELinux Policy Modules

H

ow do I disable or enable SELinux policy modules under Red Hat Enterprise Linux running on Dell hardware?

You need to use the semodule command. This command is used to manage SELinux policy modules, including installing, upgrading, listing, disabling and removing modules.

Task: See currently installed modules

Type the following command as the root user:

semodule –l

semodule -l | more

semodule | less

Sample outputs:

abrt    1.2.0

accountsd       1.0.0

ada     1.4.0

afs     1.5.3

aiccu   1.0.0

aide    1.5.0

aisexec 1.0.0

amanda  1.12.0

amavis  1.10.3

amtu    1.2.0

apache  2.1.2

apcupsd 1.6.1

arpwatch        1.8.1

asterisk        1.7.1

audioentropy    1.6.0

automount       1.12.1

avahi   1.11.2

awstats 1.2.0

bind    1.10.2

bitlbee 1.2.1

bluetooth       3.2.2

....

..

..

 Output truncated

....

..

uuidd   1.0.0

varnishd        1.1.0

vdagent 1.0.0

vhostmd 1.0.0

virt    1.4.0

vmware  2.2.0

vpn     1.12.0

w3c     1.0.0

wdmd    1.0.0

webadm  1.1.0

webalizer       1.10.0

wine    1.6.1

xen     1.9.2

xfs     1.6.0

xguest  1.0.1

zabbix  1.2.0

zarafa  1.0.0

zebra   1.10.1

zosremote       1.1.0

Task: SELinux disable module

To disable existing module, type:

 semodule -d MODULE_NAME_HERE

OR

 semodule --disable=MODULE_NAME_HERE

To disable module called webalizer, enter:

# semodule -v -d webalizer

To verify new settings, enter:

# semodule -l | grep webalizer

Sample outputs:

[root@rhel6 ~]# semodule -v -d webalizer

Attempting to disable module 'webalizer':

Ok: return value of 0.

Committing changes:

Ok: transaction number 0.

[root@rhel6 ~]# semodule -l | grep webalizer

webalizer       1.10.0  Disabled

Task: SELinux enable module

To enable existing module, type:

 semodule -e MODULE_NAME_HERE 

OR

# semodule --enable=MODULE_NAME_HERE

To enable module called webalizer, enter:

# semodule -v -e webalizer

Sample outputs:

Attempting to enable module 'webalizer':

Ok: return value of 0.

Committing changes:

Ok: transaction number 0.

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