Squid is an open source web proxy and cache server that provides content filtering, access control, and caching capabilities to improve network performance; it sits between clients and external servers to filter web traffic based on configured rules and restrictions set by the network administrator using regular expressions and access control lists. Squid can also integrate with authentication servers like ncsa_auth to require passwords for user access through the proxy.

1. SQUID

2. 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).

3. 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.

4. 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.

5. Installation of SQUID

The following command to be typed for installing
SQUID
sudo apt-get install squid

After installing SQUID , u will find it under
directory /etc/squid

The configuration file squid.conf exist under this
directory , which has to be configured essential for
1. Web Filtering
2. Authentication
3. Access Permissions to users

6. Starting the SQUID server

The following command is written to start the
server.
sudo /etc/init.d/ squid start

To , ensure that the squid server is working properly
netstat -a -n | grep 3128 (3128 is default the port
number).

7. Configuration of SQUID

The configuration file can be opened by the
following command
sudo 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

8. Configuration of SQUID

To add various constraints on the web browsing
through proxy server.We configure the squid.conf
file

To allow only particular range of IP `s , we
configure it in TAG: acl block.

acl internal_network src 192.168.0.0/24

Then we allow the http acces to the specified
internal_network in TAG: http_access block.
http_access allow internal_network

The user accesing web through the proxy server,
they have to set the IP in the given range.

9. 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 blacklist

Since specifying the list of websites is a
cumbersome process, the SQUID server is powered
with regular expression to define a general pattern .

10. Configuration of SQUID

The Regular Expression are specified in the file
named blocks.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.acl

11. 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

12. NCSA Configuration

In TAG: auth_param block , we specify the
folowwing commands.
auth_param basic program /usr/lib/squid/ncsa_auth
/etc/squid/passwd
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 1 minutes
auth_param basic casesensitive off

In TAG: acl acl ncsa_users proxy_auth REQUIRED

http_access allow ncsa_users

The above command to allow the ncpa users

13. 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.

14. 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.

15. 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)