> http://www.monodevelop.com/ — The MonoDevelop project has its own site, which is the best place to look for updates.
> http://www.icsharpcode.net/OpenSource/SD/ — MonoDevelop started life as a port of SharpDevelop. If you happen to dual-boot on Windows, this might prove very useful to you.
> http://msdn.microsoft.com/vcsharp/ — We don't print many Microsoft URLs in this book, but this one is important: It's the homepage of their C# project, which can be considered the spiritual home of C# itself.
The #1 book we refer to for C# information is Jesse Liberty's
PART VI
Fedora Housekeeping
CHAPTER 30
Securing Your Machines
No home computer with a connection to the Internet is 100% safe. If this information does not concern you, it should! Although there is no way to stop a serious cracker who is intent on getting into your computer or network, there are ways to make it harder for him and to warn you when he does.
In this chapter, we discuss all aspects of securing your Linux machines. You might have wondered why we did not spread this information around the book wherever it was appropriate, but the reason is simple: If you ever have a security problem with Linux, you know you can turn to this page and start reading without having to search or try to remember where you saw a tip. Everything you need is here in this one chapter, and we strongly advise you read it from start to finish.
Understanding Computer Attacks
There are many ways in which computer attacks can be divided, but perhaps the easiest is
In earlier days, there was a distinction made between the words
This distinction was lost on the general public, so the term
Although you should never ignore the internal threat, you should arguably be more concerned with the outside world. The big bad Internet is a security vortex. Machines connected directly to the outside world can be attacked by people across the world, and invariably are, even only a few minutes after having been connected.
This situation is not a result of malicious users lying in wait for your IP address to do something interesting. Instead, canny virus writers have created worms that exploit a vulnerability, take control of a machine, and then spread themselves to other machines around them. As a result, most attacks today are the result of these autohacking tools; there are only a handful of true hackers around, and, to be frank, if one of these ever actually targets you seriously, it will take a mammoth effort to repel him regardless of which operating system you run.
Autohacking scripts also come in another flavor: prewritten code that exploits a vulnerability and gives its users special privileges on the hacked machine. These scripts are rarely used by their creators; instead, they are posted online and downloaded by wannabe hackers, who then use them to attack vulnerable machines.
So, the external category is itself made up of worms, serious day job hackers, and wannabe hackers (usually called
On the internal front, things are somewhat more difficult. Users who sit inside your firewall are already past your primary source of defense and, worse, they might even have physical access to your machines.
Regardless of the source of the attack, there is a five-step checklist you can follow to secure your Fedora box:
1. Assess your vulnerability. Decide which machines can be attacked, which services they are running, and who has access to them.
2. Configure the server for maximum security. Only install what you need, only run what you must, and configure a local firewall.
3. Secure physical access to the server.
4. Create worst-case-scenario policies.
5. Keep up to date with security news.
These topics are covered in the following sections, and each is as important as the others.
Assessing Your Vulnerability
It is a common mistake for people to assume that switching on a firewall makes them safe. This is not the case and, in fact, has never been the case. Each system has distinct security needs, and taking the time to customize its security layout gives you maximum security and the best performance.
The following list summarizes the most common mistakes:
> Installing every package — Do you plan to use the machine as a DNS server? If not, why have BIND installed? Go through the Add/Remove Applications dialog and ensure that you have only the software you need.
> Enabling unused services — Do you want to administer the machine remotely? Do you want people to upload files? If not, turn off SSH and FTP because they just add needless attack vectors. This goes for many other services.
> Disabling the local firewall on the grounds that you already have a firewall at the perimeter — In security, depth is crucial: The more layers someone has to hack through, the higher the likelihood she will give up or get caught.
