Or you could have mice (the animals) in your house. Mice love to create nests in warm places, and your computer is pretty warm. Just imagine all those little teeth gnawing away on all of wires ...

Worse yet, imagine it rains and a leak appears directly over your hard drive ... or your "friend" spills coffee on CPU cabinet. I could go on and on about what could happen to your computer.

I don't know about you, but I spend more time on my home computer than I do watching television, reading, eating or anything else except possibly working at my day job. When my computer has a problem, especially one that results in a boot failure, I get extremely angry. I feel like I have been betrayed by my best friend. If system gets damaged, I feel just as much pain as if a good friend went into hospital.

The thing to do is to make sure you are prepared for worst possible thing that can happen ... total system failure. This is a very difficult task to write about as there are many different ways that a computer can eat itself or be eaten - perhaps as many ways as there are computers.

It is beyond scope of this article to go into great detail on how to make your system totally recoverable. There are many other great resources on internet and in documentation that originally came with your computer which will help you prepare.

Briefly, though, what you need are following:

- The CD ROM containing operating system installation files. This virtually always comes with a new system. It will be labeled something like "Windows 95" or "Windows 2000".

- Any other kind of recovery CD that came with your system.

- A bootable media. Sometimes CD ROM itself is bootable. More often, you will get one or more floppy diskettes with your system. Keep these in a safe place.

- An emergency repair disk. This is usually one (sometimes more) diskettes which contain all of configuration options for your operating system. You need to create these occasionally (they are not automatic) - usually whenever you make a major change.

There are many methods by which a hacker may attack or take control of a site. I am focusing this discussion on attacks that come via form input. That is, anywhere you have input coming in from your web user, e.g. a registration form, user login or even a search on your site. Scripts could be sent to your server by entering < script> some malicious code < /script> in your input fields. The following are steps you can take to minimise risk of this happening. These measures will not make your site hacker-proof (no site can be if a hacker really has it in for you), but it can make it less of an easy target. Step 1: Place character limits on your inputs You do this by adding "maxlength" attribute into your text input tags

e.g. < input type="text" name="firstname" maxlength="15">

The example above restricts user to a 15 character input for that field. The "< script>" and "< /script>" tags alone will take 17 characters so smaller you limit your "maxlength" attribute to, harder it will be to include rogue codes in your inputs. Of course, you must ensure that you impose a suitable limit so that actual input from your valid users will not be excluded. Step 2: Filtering your data All data received from your site should be filtered, you can either filter your data when it comes into your server as user input, or when it goes out as results for your user's browser. Whether you should filter input or output, depends on your site and its requirements, there is a good discussion on this at http://www.cert.org ech_tips/malicious_code_mitigation.html/ . Filters can be written in any language, here is an example in Perl :