Internet Security and Privacy - The Basics

First things to know... Well, what's it all about...?

Well, what's a virus... simply said, a computer virus is just a piece of normal programming code, just like any other program... but a normal program does something the user wants (at least it should do that ;-) while a virus does something the user does not want... things like blocking your system, or even worse, sending your personal information to somebody else without you even knowing it

Depending on what a "virus" precisely does, it's called a "virus", a "trojan", a "worm", a "hijacker", a "keylogger" etc.; for instance, a hijacker can reset your internet start- and search pages, a worm can infect your mail-address-book, a keylogger records each keyboard character you type and may send it to someone you don't know... and so on. But don't bother... let's call all that stuff simply a "virus", for it doesn't matter here what that crap-code is supposed to do... There are a few simple rules to avoid a lot of trouble... here they come...
Some sorts of files can be dangerous, but others can not. So if we can make the distinction between both, we've already set the first step. And luckily, there's nothing complicated about it. We'll see that by simply looking at the file name, you can already make the difference. By doing just this you've already taken the most important step to internet protection. So read on, it will be clear in a moment...

Last thing you must realize is that, in order to start working, a "virus" or other malicious code must be installed on your computer. This can be done without the user even knowing or seeing anything, but in many, many cases the user him or herself must do something to activate the virus. And then it's YOU who installs it... or not.

A little background info : something to know about files and extensions


filenames and extensions

For a better understanding, it's useful to have some basic knowledge about how files are named and how your computer works with them. You find this topic more extensively described in the info-pages on file-formats and naming conventions, but in short, here you get the things you need to know about files regarding security.
Everyfile on your computer has a name, consisting of the name itself, and a so-called "extension". That's the three (or sometimes more or less) letter-code after the filename. Filename and extension are separated by a point, which belongs to the extension. The computer uses the extensions to know what kind of file it is and what to do with it. Example: in the filename "MyLetter.doc", the filename is "MyLetter" and ".doc" is the extension.

Remark: if in Windows Explorer, those file-extensions don't show up on your computer, this simply means that your configuration is set to hide them (the default setting). To change it to show the extensions (and some other things), in Windows Explorer, go to the Options in the menu "Extra", and on the view-tab uncheck the option to hide file-extensions. You may also want to check/uncheck some other options there, resulting in a much more advanced and wider file viewing. You can do this without risk, for in case you don't want to keep the changes, you always can set them back to default by clicking the standard/default button.

If you want to learn more about file-names and extensions, see the appropriate section about file-names, extensions, file-naming and conventions on this site. It will give you a good insight in file-naming and also the necessary practical knowledge about working with graphical formats.

"non-executable" and "executable" files

Generally speaking, there are two kinds of files:

First, there are the files such as text-documents, images, spreadsheets,... mostly all the work you created and saved onto your computer. In our example above, "MyLetter.doc" could be a letter you wrote with Microsoft Word.

And now, one step further: try you see that the file (in this case "MyLetter.doc") does not really do things by itself. It must be opened with a program (in this example the word-processor Microsoft Word).

It's not a computer program itself, it does not execute commands on the system, it just contains the "data" of your text, picture, spreadsheet and so on, and to view it and work with it, you need a program.

Therefore such files are called "non-executable" (or "data") files, and -in most cases- they are pretty harmless.
Nevertheless, some "non-executable" files can make the program in which they are opened, executing malicious code or import unwanted data.

Just as an example for those who want to go deeper into the subject: this can occur respectively when opening *.doc or *.xls files containing malicious visual basic script in Word or Excel, and when opening *.reg or *.key files which can import unwanted entries in the system registry.

But don't bother this techno stuff thing... just read on and then afterwards, look for the extension-list, it will help you to avoid nearly all trouble without much techno-talk...

Now comes the second kind of files: all those programs used to view your work, they also are build of files. But those files contain the program-code to do things on your computer, good or bad... They make the system work, they do something by executing commands. So they are called "executable" (or "program") files and in most cases they have the extension *.exe.
And of course, they can do harm. Remember, while a good program does the things we want, a virus is just a normal program, but doing lots of things we don't want. So a file with extension *.exe maybe good or bad.

So in our example, in order to view the file "MyLetter.doc" (containing the text) it must be opened within a program (in this case the word-processor Ms Word). The program can be considered as the "executable" (with extension *.exe), while the text-file is not, it's a "non-executive" file... See the difference?

How do you know if a file can be dangerous or not...?

Well, that's simple... supposing that you've read the text above or you already know something about files.

Just like any other file on your computer, a "virus" has a filename, consisting of the name itself and an extension. By looking at the extension, you can always see if a file is "safe" or not.
If the extension belongs to a kind of file which is always safe, okay no problem, just open it. If the extension belongs to a file-type which maybe harmfull, then it depends on the source from where you got that file. If you got it from a legitime and safe source (e.g. the original files installed by your Windows operating system or by your official programs) then of course there's no problem.
But if you downloaded the file from the internet or if you got it by e-mail (even from someone you know!), then you can't trust that file.
Hey... wait a moment: "even from someone you know" remember... Think about this: someone could have send you a virus without even knowing, so don't consider a file to be safe 'cause you know the person who has send it to you.
Now all you need is a list of "safe" and "potentially dangerous" file-extensions. Although such a list will never be complete 'cause there are hundreds of file-formats (extensions) and many of them are program-dependent, or so rare you'll never see them, it will be a big help to avoid most of the common infections on the internet.
You find such a list in the next security topic: "the potentially dangerous file list". You can go there now, but hey, read on first...
Important: of course, you must check the extension before opening or double-clicking the suspicious file. For once you opened the file, you can't stop it from opening or running. And be careful, you don't get another chance once you've opened the file.

How to handle potentially dangerous files

In case you received a potentially dangerous file without you explicitely asking for it yourself (such as receiving suspicious files as an e-mail attachment), simply delete it without opening. And don't be curious to see what's in it. There's no reason to send you such a file without your permission, and you won't miss anything. As long as you don't open (double-click) the file, nothing has happened.

If you downloaded the file from the internet, or if you've got it from a magazine-cd or from a friend and so on... just use some common sense... If you downloaded the files from a well-known site (e.g. a well-known software-library or vendor) then the files will be practically always safe. If the files do not come from a such a trusted source, then ask yourself if it all is worth the risk...
And then it's good practice to use a virus-scanner to check them before opening. But remember, lots of new virii are newly coming to the internet each day, so each virus-scanner program must be updated frequently. You can have a look in the computing software section for virus-scanner programs and other security software.




Related topics : E-mail security and privacy - Web security and privacy - The "potentially dangerous file" list


back to the top



All info provided on an "as is"-basis, without any warranty and/or further responsibility whatsoever.
All texts are free for personal non-commercial use. Copyright by the NightOwl.