Squid Proxy Installation and Configuration

Squid

Squid is a most popular caching and forwarding HTTP web proxy server. It is used to cache web pages from 
a web server to improve web server speed, reduce response times and reduce network bandwidth usage.

Installation of Squid in Ubuntu:
sudo apt update    --To update ubuntu.
sudo apt -y install squid
sudo systemctl start squid
sudo systemctl enable squid
sudo systemctl status squid

Squid configuration file: /etc/squid/squid.conf
Squid Access log: /var/log/squid/access.log
Squid Cache log: /var/log/squid/cache.log

Configure Squid:
vi /etc/squid/squid.conf

http_port : This is the default port for the HTTP proxy server, by default it is 3128, you may change 
            it to any other port that you want, you may also add the “transparent” tag to the end of 
            the line like http_port 8888 transparent to make Squid proxy act like a transparent proxy if you want.
            
http_access deny all : This line won’t let anybody to access the HTTP proxy server, that’s why you need to change 
            it to http_access allow all to start using your Squid proxy server.
            
visible_hostname : This directive is used to set the specific hostname to a squid server. You can give any hostname to squid.


Restart Squid:
sudo systemctl restart squid


Configure squid as an HTTP proxy using only the client IP address for authentication. To allow only one IP address to 
access the internet through your new proxy server, you will need to define new acl (access control list) in the configuration file.

vi /etc/squid/squid.conf
acl localnet src XX.XX.XX.XX
Where XX.XX.XX.XX is the IP address of client machine. This acl should be added in the beginning of the ACL’s section.
Example: acl localnet src 192.168.0.102  #Boss IP address, Some comments

You will need to restart Squid service to take the new changes into effect.
$ sudo systemctl restart squid

Open Ports in Squid Proxy. By default, only certain ports are allowed in the squid configuration, add like below: 
acl Safe_ports port XXX    --Where XXX is the port number that you wish to allow. 


Block Websites:
sudo touch /etc/squid/blacklisted_sites.acl    --Create a file
.badsite1.com    --File content
.badsite2.com    --File content
Squid will block all references to that sites including www.badsite1, subsite.badsite1.com etc. 

acl bad_urls dstdomain "/etc/squid/blacklisted_sites.acl"
http_access deny bad_urls



Block Specific Keyword with Squid
sudo touch /etc/squid/blockkeywords.lst
    facebook
    instagram
    gmail

acl blockkeywordlist url_regex "/etc/squid/blockkeywords.lst"
http_access deny blockkeywordlist

sudo systemctl restart squid

Configure Proxy in Browser now to hit Squid:
Open Firefox and go to Edit –> Preferences –> Advanced –> Network –> Settings and select “Manual proxy configuration”.

Hint: https://www.tecmint.com/install-squid-in-ubuntu/