Transparent proxy servers sit between clients and the Internet, intercepting all requests without requiring client-side configuration. A popular software solution for implementing a transparent proxy is Squid. In this article, we will go over the process of setting up Squid on Ubuntu and Debian systems.
- A system running Ubuntu or Debian.
- Root or sudo access.
Update your system's package list.
sudo apt-get update
sudo apt-get install squid
Back up the original configuration file. This is always a good practice.
sudo cp /etc/squid/squid.conf /etc/squid/squid.conf.original
Edit the configuration file.
sudo nano /etc/squid/squid.conf
To configure a basic transparent proxy, make the following changes in the configuration file:
Find the line http_port 3128 and change it to:
http_port 3128 intercept
Allow local network access to the Internet. Replace YOUR_NETWORK with the CIDR of your local network, for example 192.168.1.0/24.
acl localnet src YOUR_NETWORK http_access allow localnet
Save the file and exit the editor.
For the proxy to function as a transparent proxy, all web traffic must be redirected to go through it. This can be done using iptables.
Redirect HTTP traffic (port 80) to Squid.
sudo iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j DNAT --to 127.0.0.1:3128
Replace eth0 with your network interface if it's different.
Make sure the iptables rules persist after a reboot. One way to achieve this is to install iptables-persistent.
sudo apt-get install iptables-persistent
During installation, you will be asked to save your current rules. Choose "Yes" for both IPv4 and IPv6 rules.
Start and test
Restart Squid to apply the changes.
sudo systemctl restart squid
Check the status of Squid.
sudo systemctl status squid
Test the configuration by attempting to access the Internet from a client computer. You shouldn't need to do any client-side configuration if everything is set up correctly.
Monitoring and logs
To get detailed information about accessed websites, Squid provides logs. The access log can be checked on:
A transparent proxy can be beneficial for several reasons, such as bandwidth management, content filtering or monitoring. Squid offers a powerful solution for this purpose. While the previous steps provide a basic setup, Squid offers several advanced features and configurations worth exploring to meet your specific needs.