In Windows, typing

IPCONFIG /ALL

produces:

Windows IP Configuration

Host Name . . . . . . . . . . . . : host-name

Primary Dns Suffix  . . . . . . . :

Node Type . . . . . . . . . . . . : Unknown

IP Routing Enabled. . . . . . . . : No

WINS Proxy Enabled. . . . . . . . : No

DNS Suffix Search List. . . . . . : domain.local

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix  . :

Description . . . . . . . . . . . : Realtek RTL8168C(P)/8111C(P) PCI-E Gigabit Ethernet NIC

Physical Address. . . . . . . . . : 00-24-XX-XX-XX-XX

Dhcp Enabled. . . . . . . . . . . : Yes

Autoconfiguration Enabled . . . . : Yes

IP Address. . . . . . . . . . . . : 64.XXX.XXX.220

Subnet Mask . . . . . . . . . . . : 255.255.255.0

Default Gateway . . . . . . . . . : 64.XXX.XXX.1

DHCP Server . . . . . . . . . . . : 209.XXX.XXX.135

DNS Servers . . . . . . . . . . . : 208.67.222.222 208.67.220.220

Lease Obtained. . . . . . . . . . : Thursday, January 07, 2010 12:42:26 PM

Lease Expires . . . . . . . . . . : Thursday, January 07, 2010 8:42:26 PM

You can plainly see all the information you need to know. How do you do that in Linux? Well, the answer depends on which distro you are using and which packages you are using, but here are some answers:

“route -nee” produces (Some fields have been chopped off):

Kernel IP routing table

Destination     Gateway         Genmask

192.168.100.0   0.0.0.0         255.255.255.0

69.XXX.XXX.0    0.0.0.0         255.255.255.0

169.254.0.0     0.0.0.0         255.255.0.0

0.0.0.0         69.XXX.XXX.1    0.0.0.0

“ip route show” produces:

192.168.100.0/24 dev eth0  proto kernel  scope link  src 192.168.100.101

69.XXX.XXX.0/24 dev eth1  proto kernel  scope link  src 69.XXX.XXX.225

169.254.0.0/16 dev eth1  scope link  metric 1000

default via 69.XXX.XXX.1 dev eth1  metric 100

“ifconfig” produces:

eth0      Link encap:Ethernet  HWaddr 00:d0:b7:3c:dd:4f

inet addr:192.168.100.101  Bcast:192.168.0.255  Mask:255.255.255.0

inet6 addr: fe80::2d0:b7ff:fe3c:dd4f/64 Scope:Link

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

RX packets:18365 errors:0 dropped:0 overruns:0 frame:0

TX packets:15981 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:1987703 (1.9 MB)  TX bytes:11111362 (11.1 MB)

eth1      Link encap:Ethernet  HWaddr 00:1a:4d:94:75:43

inet addr:69.XXX.XXX.225  Bcast:69.XXX.XXX.255  Mask:255.255.255.0

inet6 addr: fe80::21a:4dff:fe94:7543/64 Scope:Link

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

RX packets:59590 errors:0 dropped:0 overruns:0 frame:0

TX packets:11997 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:11600972 (11.6 MB)  TX bytes:3977507 (3.9 MB)

Interrupt:23 Base address:0×6000

lo        Link encap:Local Loopback

inet addr:127.0.0.1  Mask:255.0.0.0

inet6 addr: ::1/128 Scope:Host

UP LOOPBACK RUNNING  MTU:16436  Metric:1

RX packets:4709 errors:0 dropped:0 overruns:0 frame:0

TX packets:4709 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0

RX bytes:1042664 (1.0 MB)  TX bytes:1042664 (1.0 MB)

“cat /etc/resolv.conf” produces:

#Open DNS

nameserver 208.67.222.222

#Google DNS

8.8.8.8

#Open DNS

nameserver 208.67.220.220

#Google DNS

8.8.4.4

That should give you the information you need.

Content Filtering

(Ubuntu 9.10)

Objectives:

1. Add content filtering to an existing Ubuntu system.

2. Prevent user from bypassing the filtering system.

Software:

Open a terminal and type:

user@system:~$ sudo apt-get install iptables dansguardian squid

Configuration:

1. Squid

Open a terminal and type:

user@system:~$ sudo gedit /etc/squid/squid.conf

change this line:

http_port 3128

to

http_port 3128 transparent

Save file then open a terminal and type:

user@system:~$ sudo /etc/init.d/squid restart

2. Dansguardian

Open a terminal and type:

user@system:~$ sudo gedit /etc/dansguardian/dansguardian.conf

change this line:

UNCONFIGURED

to:

#UNCONFIGURED

Save file then open a terminal and type:

user@system:~$ sudo /etc/init.d/dansguardian start

3. Test Proxy

Open Firefox

Go to http://tits.com or other known bad site.

The site should display.

Now in Firefox select

Edit > Preferences > Advanced > Connection > Settings

Select Manual proxy configuration

In the HTTP Proxy box type: 127.0.0.1 Port: 8080

Place a Check in the box labeled Use this proxy server for all protocols

Click OK then Close

Go to http://google.com and Google should be displayed. Click Refresh and verify it’s still working.

Go to http://tits.com or other known bad site.

The site should show as blocked. You may have to hit refresh for this to work.

At this point, the proxy is working.

Now in Firefox select

Edit > Preferences > Advanced > Connection > Settings

Select No proxy

Click OK then Close

4. Test iptables

iptables is the firewall for Ubuntu. If you are using a firewall front end such as shorewall, etc. then you will have to adapt the concept below to your particular configuration. On a clean install of Ubuntu, this will work as written.

Open a terminal and type:

user@system:~$ sudo iptables -t nat -A OUTPUT -p tcp -m owner ! –uid-owner proxy –dport 80

-j REDIRECT –to-port 8080

This tells the firewall that outgoing web requests requested that are made by anyone other that the proxy should be redirected to the proxy

Open Firefox

Go to http://tits.com or other known bad site.

The site should show as blocked. If so, the firewall is correctly configured as a transparent proxy.

Now, to make the changes permanent.

Open a terminal and type:

user@system:~$ sudo gedit /etc/init.d/tproxy

Add this line:

iptables -t nat -A OUTPUT -p tcp -m owner ! –uid-owner proxy –dport 80

-j REDIRECT –to-port 8080

Save and exit.

Issue this command to make the file executable:

user@system:~$ sudo chmod a+x /etc/init.d/tproxy

Issue this command to make the above script run at startup:

user@system:~$ sudo update-rc.d tproxy

That’s it.

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