This book focuses its attention on securing your Linux server. Linux has become one of the most used Operating system, if not the most used, across the world and all over the Internet.Most web servers run on Apache and Linux, a lot of MTAs also run Postfix or Sendmail and they both run on Linux. With the advent of broadband, more and more home users are setting up their web servers and leaving it always connected to the Internet.A few years ago (about 15) years, I had set up a Linux router for my Internet at home, I left the default configuration, just because a) I did not want to spend too much time making it secure (I did not think anyone would have an interest in my router) b) I was lazy c) I did not care much. So the story goes, my Internet became slow, and I started to investigate the issue. I managed to track the slowness to my Linux router; it had been targeted, by multiple requests and attempts to break in, trying the root password. I examined the /var/log/messages log, and there were 200000 failed attempts to log in to my router, which sparked my desire to become an expert in Cyber Security, this is to show that we all need to take security seriously. There are so many different aspects of security, and I will try to cover most of them. If you take it seriously, you will try and implement most of my recommendations if not all; your server is exposed, and connected to the Internet is a constant danger.A considerable amount of exploits and vulnerabilities are discovered on a daily basis. As soon as a new vulnerability is found, it gets used right away by hackers.I believe we all have responsibilities with our security, also with our customers, to the company we work for, etc. etc. This book is about Linux Security, but its ideas within will be helpful to protect almost any server or operating system. As you probably have seen on TV and news, pretty much daily we hear or see different stories; compromised servers, scammed users and companies losing customer data and so many horrible things.While there is no such thing as a silver bullet, we can certainly do a lot to make it harder for cybercriminals to gain access to our Linux servers. It is our responsibility to lock every single door we can think of and keep our eye open to logs and any unusual behaviour of our servers.A lot of this information you can find online, but I am writing it organized in a way which is specific to make our Linux servers, more secure from the physical aspect to the OS, to the admin tasks and some applications. I am going to describe each section, talk about reasons and tell you which settings to adjust and show you how to set them up. I will try and explain each configuration setting.I think security is a fascinating subject, and we need to be more aware of what we can do to improve it. There are so many aspects, but it is essential to raise barriers, the more, the better.This book covers a lot of aspects of Linux security, if you follow it through, your server will become much more secure, and you should have fewer issues with it or them. This book does not cover network design security, networking, or network segmentation. This book is about Linux security.I think you won't be disappointed in buying this book, we covered a lot of ground and put a lot of effort in making it as accurate as possible, and covering as many aspects as possible.