Ubuntu

In this recipe, we will look at some best practices to secure Ubuntu systems. Linux is considered to be a well secured operating system. It is quite easy to maintain the security and protect our systems from unauthorized access by following a few simple norms or rules.

Getting ready

You will need access to a root or account with sudo privileges. These steps are intended for a new server setup. You can apply them selectively for the servers already in productions.

How to do it…

So you have installed minimal setup of Ubuntu, you have setup SSH with public key authentication and disabled password authentication, and you have also allowed only single non-root user to access the server. You also configured a firewall, spending an entire night understanding the rules, and blocked everything except a few required ports. Now does this mean that your server is secured and you are free to take a nice sound sleep? Nope.

It is said that the best way to improve server security is to reduce the attack surface. Network communication in any system happens with the help of logical network ports, be it TCP ports or UDP ports. One part of the attack surface is the number of open ports that are waiting for connection to be established. It is always a good idea to block all unrequired ports. Any traffic coming to these ports can be filtered, that is, allowed or blocked with the help of a filtering system.

VPN enables two or more systems to communicate privately and securely over the public network or Internet. The network traffic is routed through the Internet, but is encrypted. You can use VPN to set up a secure connection between two datacenters or to access office resources from the leisure of your home. The VPN service is also used to protect your online activities, access location restricted contents, and bypass restrictions imposed by your ISP.

Networking consists of various components and services working together to enable systems to communicate with each other. A lot of times it happens that everything seems good, but we are not able to access other servers or the Internet. In this recipe, we will look at some tools provided by Ubuntu to troubleshoot the network connectivity issues.

Getting ready

As you are reading this recipe, I am assuming that you are facing a networking issue. Also, I am assuming that the problems are with a primary network adapter, eth0.

Transmission Control Protocol and Internet Protocol (TCP/IP) is a standard set of protocols used by every network-enabled device. TCP/IP defines the standards to communicate over a network. TCP/IP is a set of protocols and is divided in two parts: TCP and IP. IP defines the rules for IP addressing and routing packets over network and provides an identity IP address to each host on the network. TCP deals with the interconnection between two hosts and enables them to exchange data over network.

When an application becomes popular, it sends an increased number of requests to the application server. A single application server may not be able to handle the entire load alone. We can always scale up the underlying hardware, that is, add more memory and more powerful CUPs to increase the server capacity; but these improvements do not always scale linearly. To solve this problem, multiple replicas of the application server are created and the load is distributed among these replicas.

Network Time Protocol (NTP) is a TCP/IP protocol for synchronizing time over a network. Although Ubuntu has a built-in clock that is helpful for keeping track of local events, it may create issues when the server is connected over a network and provides time-critical services to the clients. This problem can be solved with the help of NTP time synchronization. NTP works by synchronizing time across all servers on the Internet.

In this recipe, we will install and configure the squid proxy and caching server. The term proxy is generally combined with two different terms: one is forward proxy and the other is reverse proxy.