Different Methods Through Viruses Maybe Transferred

There are different methods through viruses may be transferred from one computer to another.

1. Now- a-days, most of the viruses spread due to receiving unknown e-mail messages that contains viruses. When a user opens such an infected message, the virus is also loaded into the computer memory. In this way, many other program files loaded into the memory are infected. This virus is also transferred to other computers when e-mail messages are sent from the infected computer to them. Due to these viruses, some time an auto generated email message from your email ID sends to your friends from your side with different virus messages. Never open unknown and attractive subject line email messages, always scan first even if you know the sender of the message.
   
2. Another way of spreading virus is by using Internet and other networks. For example, when you download infected executables files or data files from the Internet or from a shared disk on the network, viruses are transferred to your computer. It must be noted that many software are available on the Internet with free of cost. Most of that software contains viruses, for example free PHP or ASP scripts are the main source of virus, always get these scripts from reliable sources. In an LAN, if a computer contains a virus, then all the computers on the network may be infected with that virus.
   
3. One important means of exchanging data is through the use of removable media like, CDs, MP3 player, ipod and flash devices. So, when you copy the data from one computer to another by using a removable media, the viruses are also transferred.
   
4. The virus can also infect your computer by using pirated software. The software, which is installed into your computer without license is referred to as pirated software. Some companies may intentionally attach some virus programs into their software. This program will only activate when it does not find some special files like license files on your computer.

What kind of attachments can contain viruses

Basically, anything that is executable (able to run). You're generally safe with picture files, text files, and the like. However, it still pays to scan first.

Here is a very short list of the most common to watch out for:

exe
zip
scr
vbs
bat
com
pif
asp
doc
xls

Those are the most common; don't misinterpret this to mean that if you get one of these files it's automatically a virus. A ".zip" file may be nothing more than a set of compressed files your friend sent you to look at. A "doc" or "xls" file may simply be an MS Office file. It's just that these type of files could also be viruses.

A couple other virus tricks you need to be aware of. First, MS Office files can contain what are called "Macro Viruses". Without getting into too much detail, these files can run a "macro" (a macro is a mini-program run from within another program) that can be as destructive as any "regular" virus. So, my advice on MS Office attachments is not to open them unless you are expecting them. If they just show up, verify with the sender first.

The other trick you need to look out for is an extra extension added to an attached file. For example, you may have something like "mypicture.jpg.vbs". In fact, if you don't have your computer set to view file extensions, it may just look like "mypicture.jpg" and omit that last "vbs" part.

This may appear to be a jpg picture file, but it's actually a Visual Basic Script file. If executed, it will happily infect your computer with a virus.

So, be careful out there.