SQUID

Squid – A HTTP 1.0 Proxy Server

Squid is a web based proxy server based on harvest cache demon , built in 1990`s.

A proxy server is an intermeadiate server for the clients , which seeks resources from other server (NET).

Why Web proxy ....?

The developers of the HTTP protocol and the web analyst envisioned that , there would be an exponential growth in web content.

There was a need of efficient distribution mechanism and powerfull caching primitives as well as not comprimising the security of the network.

In the pursuit of developing content distribution and at the same time securing the web server , SQUID was evolved.

Web Filtering using SQUID

SQUID works on content catching mechanism , by cached content the information will be fetched locally thus saving the bandwidth for ISP (internet service providers).

SQUID filters the request from the users and fetched the desired outcome.

The constraints on filtering and access permissions will be set by the network administrator .

Filtering conditions is set using Regular Expressions.

Installation of SQUID

The following command to be typed for installing SQUID

sudo apt-get install squidsudo apt-get install squid After installing SQUID , u will find it under

directory /etc/squid/etc/squid The configuration file squid.confsquid.conf exist under this

directory , which has to be configured essential for

1. Web Filtering

2. Authentication

3. Access Permissions to users

Starting the SQUID server

The following command is written to start the server.

sudo /etc/init.d/ squid startsudo /etc/init.d/ squid start To , ensure that the squid server is working properly

netstat -a -n | grep 3128netstat -a -n | grep 3128 (3128 is default the port number).

Configuration of SQUID

The configuration file can be opened by the following command

sudo gedit /etc/squid/squid.confsudo gedit /etc/squid/squid.conf The config files is structured into tags. The essential tags are

1. TAG: auth_param

2. TAG: http_access

3. TAG: acl

Configuration of SQUID To add various constraints on the web browsing

through proxy server.We configure the squid.confsquid.conf file

To allow only particular range of IP `s , we configure it in TAG: acl block.

acl internal_network src 192.168.0.0/24acl internal_network src 192.168.0.0/24 Then we allow the http acces to the specified

internal_network in TAG: http_access block.

http_access allow internal_networkhttp_access allow internal_network The user accesing web through the proxy server,

they have to set the IP in the given range.

Configuration of SQUID

To filter the web content and not allow the users of the proxy server to access the web pages , A file has to be created in the SQUID folder and the list of websites to be blocked is added .

In the TAG: http_access we deny the access.

http_access deny blacklisthttp_access deny blacklist Since specifying the list of websites is a

cumbersome process, the SQUID server is powered with regular expression to define a general pattern .

Configuration of SQUID

The Regular Expression are specified in the file named blocks.file.aclblocks.file.acl .

\.[Ee][Xx][Ee]$

\.[Aa][Vv][Ii]$

\.[Mm][Pp][Gg]$

\.[Mm][Pp][Ee][Gg]$

\.[Mm][Pp]3$ In the TAG: http_access we deny the access.

http_access deny blocks.file.aclhttp_access deny blocks.file.acl

Web Page Authentication

Squid associating with ncsa_auth program can be used to assign user name and password.

To create user authentication htpasswd /etc/squid/passwd user1

To change the read file premission chmod o+r /etc/squid/passwd

You can verify it by locating it on /usr/lib/squid/ncsa_auth

NCSA Configuration

In TAG: auth_param block , we specify the folowwing commands.

In TAG: acl acl ncsa_users proxy_auth REQUIRED http_access allow ncsa_usershttp_access allow ncsa_users The above command to allow the ncpa users

auth_param basic program /usr/lib/squid/ncsa_auth auth_param basic program /usr/lib/squid/ncsa_auth /etc/squid/passwd/etc/squid/passwdauth_param basic children 5auth_param basic children 5auth_param basic realm Squid proxy-caching web serverauth_param basic realm Squid proxy-caching web serverauth_param basic credentialsttl 1 minutesauth_param basic credentialsttl 1 minutesauth_param basic casesensitive offauth_param basic casesensitive off

What not to Expect from SQUID..?

SQUID is not a NIDS/NIPS (Network Intrusion Detection/Prevention System).

You cannot monitor live network packets. Although there are other network tools which can be associated with them.

Which Section of people does squid appeal to....?

In colleges and schools. In Small IT industries where network security is not

their prime prioriy. Other organizations where hardware firewalls like

CISCO is not feasible and they look forward for a simple solution.

Parental Control.

Thank YOU...! This is not the end ........ There are other programs to

enhance network security like 1.SNORT

2. BASE (Basic analysis and Security Engine)

3. Honeyd Admin Interface.

For further queries u can contact us mailme@himanshuarora@co.cc (Himanshu) rahul8590 @ gmail.com (Rahul)