A first question and a short introduction from a very newbie:
As an 57 year old bloke who has grown up with Windows (starting with MS DOS, Win 3.11, Win95 thru Vista) I have come to the conclusion that it was time to try Linux, because I got fed up with regularly re-installing Windows and running various other programs to keep virussen, spyware, malware etc out of my computer.
On a separate computer I am trying out various Linux distributions and live CD's; I still have not made up my mind, but I will get there!
I have read that Linux is relatively "safe" from virusses, but it is still recommended to run an anti virus program such as Clam AV.
Q1: Is it necessary to have an AV program and is Clam AV a good solution for Linux ?
Also a problem in Windows is that with installing, deleting and re-installing software the Windows registry grows and grows and becomes polluted.
Q2: Does Linux also has something like a registry? I have tried to find this out, but I have not found yet anything specific about this. On the other hand there is also so much one can read about Linux..
If not, does this mean that if you uninstall a program everything of that program is gone? Like the MS DOS programs which are deleted if you remove the specific directory.

Greeting from peterha.

More than 95% of all viruses are written for windows, and will not execute on a linux system. The default in linux, when you download any file, is it is marked non-executable. The user,you has to change that in order for it to run, then start it up.

So, the other 5%, Mac OS, and a very few linux ones. I have ( I got a year on you ) run linux now for 6 years, never seen a virus. I do have ClamAV installed. If you dual boot, then you can use linux to scan and clean up your windows partitions. It is safe practice to have it, and run it on occasion. Your e-mail will contain viruses most often, the windows kind, that can not hurt your linux system. Let clamav remove them.

Registry? Forget that with windows, there isn't such a cluge in linux. I test lots of linux software, there can be problems installing and removing, but not any registry to be concerned about.

These days linux is getting much easier to install and maintain. I move from one release to another, just to get the latest. I also have a six year old release on an old system that still works the way it did when it was first installed.

You should run a firewall, mine is in my router. If you are directly connected to the internet, ( no router ) then run one of the many firewalls linux can provide.

Have fun with linux. I run Mandriva. Easy to install, great online software respritories, good users group. Nice built in tools to support the system. It will run as a live CD.

Have fun...

I've run Linux for several years now and I've never used antivirus products. Most antivirus programs for Linux, simply check for Windows viruses, so they are useful if you share files with Windows machines or if you are running a mail server. If you don't engage in any of these activities, then I think there is very little use for antivirus on Linux. You should make sure you have a firewall running and regularly check for rootkits because whilst Linux is very resilient against viruses and malware, crackers are a problem, just like in other operating systems. Clamav is one of the popular virus checkers for Linux systems, so if its been recommended to you, then give it shot. Also look at rkhunter and chkrootkit for detecting rootkits.

Linux itself does not have a registry and most configuration is done using text files. GNOME (one of the desktop environments) has something that resembles a registry, but thats not for Linux as a whole. Its used to configure various advanced GNOME settings. The linux package managers usually remove everything. If you alter configuration files, they may not be automatically removed, but you can use a switch to tell the package manager to remove them if thats what you want.

Mostly you run a virus scanner in Linux to prevent the spread of Windows virus to a other Windows machine or you re own when you are dual booting
A windows virus can not run under Linux
There are Linux virus but if you compare it with Windows than it is just a fraction
A good policy in Linux never log in as root , you need root privilage
to install
If you wish to do some think against this nasty stuff well run Clam AV and maybe the rkhunter too

Because of the differences between Linux and Windows design, features & user habits -- and because of the diversity of Linux distro's -- Linux users are advantaged by "herd immunity". Even if one user gets a rare Linux "virus", it may not be able to replicate. The greatest advantage is that, using Linux, almost all of the software you run is Open Source, vetted and packaged by your distribution. A programmer can't sneak in a trojan horse without being noticed. In windows, it's normal practice to search for software on the internet, and run a binary installer, installing executables and libraries who's contents only the author knows. A common trick is to publish a video, which is really unplayable, and offer a video codec to play it.

You still need to be on guard for two types of threats. Rootkits & crackers attacking exposed services.

There are two programs that scan for root kits in Linux. rkhunter and chkrootkit. These tools (and similar tools in Windows) are best run from a live distro instead of in a running system. This is because rootkits can hide themselves by replacing programs like "ps" and "ls" and replacing an lkm (Linux Kernel Module).

You can still make mistakes allowing crackers or script kiddies to "own" your computer. Run a firewall. Apply updates on your computer & your equipment (such as NAT routers). Minimize services you don't need. Never run uPnP on a router. Change default username/passwords. Don't use WEP. Do use WPA if you use wireless and use a random password. Secure services you use such as SSH or MySQL.

Spyware was invented by shareware authors as a revenue model. In windows, programs like Windows media player have these features built in by design. A propriety program may even modify the MBR or run a small root kit as part of it's protection scheme (Adobe & Sony are two examples). Contrast this with a programmer who had a "call home" feature in a library submitted to CPAN. He was quickly banned even though the intent and effect wasn't malicious.

As you install more programs, you will want to watch the size of the /usr directory. This is where programs and libraries are installed.

About the Registry Question
Configuration files are stored in the /etc directory. Sometimes the install script may modify a configuration file. This can cause a situation similar to registry corruption, but lately, instead a single file is dropped into a configuration directory. For example, installing a service like ftp might have edited /etc/xinetd.conf. Now, a file named "ftp" will be dropped into /etc/xinetd.d/ instead. If the packager made a mistake, it won't damage the settings for other services.

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Some types of attacks are against web services. If you live in the web browser sandbox, you can still be harmed yourself even if the system itself is safe. Observe the same precautions such as previewing links before clicking them, not clicking on links in emails or opening attachments unless you are expecting them, or the context of the message proves to you that the sender is someone you know and not a spambot spoofing the email address, etc.
. Maybe there is a lesson there about "cloud computing".

Thanks for all your answers. They make some more clear to me.
I still have trouble finding documentation especially for newcomers like me, but: 'keep searching and you will find' (I hope).
As I mentioned, I still have not decided on which distro; there are so many of them. I am trying out many distributions, installing them on a separate computer but all have their "charms". I am only lookin to distro's with KDE.
I want to change completely from Windows to Linux and I don't run (mail)servers of any kind; so installing software to check my Windows on viruses will hopefully be the past.
Does anyone know which small Linux distro I can use for my wife's computer who will only use the Internet for Hyves and check on mail?
So no need for a heavy install of all sorts of programs. The computer she has is a 900 Mhz DELL with 40GB harddisk.
I already have a router with a built in firewall, but I will pay extra attention to find out if it is all properly configured.
Thanks again.

Check out The Linux Documentation Project, you can read online or download stuff in .pdf or .html format:
http://tldp.org/guides.html

For newbies, I recommand UBUNTU or FEDORA since these distributions are easy to install and maintain, and they have a great online documentation. If you want to use KDE (well.. why not), you can do it with any distribution by installing it after the system install, but there is KUBUNTU which use it by default.

For your wife computer, maybe it's another story, try XUBUNTU which use a lightweight desktop manager (xfce is its name), but if it's always too heavy for such a configuration, search for a distribution like "DamnSmallLinux" or any other distributions tailored for old computer, a look at www.distrowatch.com could be a good start point. But don't download an old linux distribution for this purpose, in fact you can use last softwares technologies (read bug correction, performances increases and new fonctionnalies) with your old computer, it's just a matter of configuration.

Another thing I want to point out is that _ALWAYS_ use the provided package manager to install new softwares, forget your old habit to search and install by the hand the software you want.

Welcome to the linux world, I hope you'll enjoy it.

Thanks for your answers and advises. The Linux Documentation Project provides -as far as I can already see- much information. I shall be busy reading much of it.
Hope to find a definite Linux distribution soon. I'll be back.

Well, here I am again.
I am still looking at some distro's and I am looking into Debian, Kubuntu and I also have SlackWare in sight.
I have downloaded that software and am installing them to check them out.
But now I have some more questions and I have trouble finding an answer in the vast amount of documents, faq's etc.
Q1: Does your harddisk need to be defragmented when using Linux?
Q2: I have installed Debian with Gnome and music cd's and some DVD's are played upon putting the CD/DVD in the drive. Only when I insert an original DVD in the player, a mesage comes up and says that the source seems to be encrypted and asks if I am trying to play an encrypted DVD without " libdvdcss". What is the problem? And how can I tackle it?
Q3. When I run Linux with KDE neither CD nor DVD cannot be found and will not be played. What do I need to do or where can I find what to do? Install drivers?
I find the switch from Windows to Linux hard but I am trying..

Q1: Does your harddisk need to be defragmented when using Linux?

No. Linux filesystems do not need to be defragged.

Q2: I have installed Debian with Gnome and music cd's and some DVD's are played upon putting the CD/DVD in the drive. Only when I insert an original DVD in the player, a mesage comes up and says that the source seems to be encrypted and asks if I am trying to play an encrypted DVD without " libdvdcss". What is the problem? And how can I tackle it?

Google for libdvdcss. You'll need that to decrypt DVDs.


Q3. When I run Linux with KDE neither CD nor DVD cannot be found and will not be played. What do I need to do or where can I find what to do? Install drivers?

You're probably missing the needed codecs to play them. How they are installed just depends on which distro you're using and has little to do with KDE itself. Once you settle on a distro, then tackle those issues. Going through it just to decide to change distros would be a waste of time.

Just to reinforce, always use the pkg manager supplied with your distro to install/update software. This ensures clean software and automatically handles dependencies for you.

Here's a good guide to Linux, and a comparison of MS v Linux concepts:

http://linux.oneandoneis2.org/LNW.htm
http://rute.2038bug.com/index.html.gz

Go to the forum for your distro (The forums on this site) and read the sticky at the top. It will contain instructions for adding a repository that has the media packages you need to use for mp3 & dvd playback. There is a packman site for SuSE, a Livna site for Fedora Core and a PLF site for Mandriva. By adding the repository as one of your sources, you can use your package manager as you normally would to install media related packages.