Causes of Viruses
Following are the means through which a virus reaches from one computer to another.
- Email: Now a days, most of the virus programs spread by attaching themselves with email messages. When a user opens such an infected message, the virus is also loaded into the computers memory and attaches copies of itself with many files. Then this virus gets itself attached with email message sent from the infected computer and infects other computers
- Networks: Another way of spreading virus is by using Internet and other Networks. For example when you download some executable file or data from the Internet or from a shared disk on the Network, the infected files may be attached with the downloaded data that ultimately infects the computer.
- Removable Storage media: One important means of exchanging data is through the user of removable media like floppy disks, CDs and flash devices. So, when you copy the data from one computer to another by using a removable media, the infected files may get transferred.
- Pirated Software: Another important but not so common way the virus infects your computer is through the use of pirated software. Some companies may intentionally put some virus program into their software .This program will only activate when it does not find some special files like license files on your computer.
Types of Virus
Following are some important types of viruses:
- Boot Sector Virus: We know that the disk is divided into tracks and sectors. The disk on which the operating system has been loaded, has a special program in its first sector called the boot sector. When the computer is turned on, the program in the boot sector is automatically loaded into the memory. This program then loads the operating system into the memory after performing some initial tasks. The boot sector virus modified the program in the boot Sector and is loaded into memory whenever computer is turned on. The virus is attached with executable files i.e.exe, .com and .dl files. When the user uses these executable files, the virus attached with these files is also activated and then it infects other files and also performs destructive commands and destroy the data files also.
- Chernobal Virus : The famous chernobal virus deletes all the Microsoft office files and also the partition information from the disk hence causing a major loss of data..
- Logic Bomb: Logic bomb, differ from other viruses in that they are set to go off at a certain date and time. A disgruntled programmer, for a defense contractor created a bomb in a program that was supposed to go off two months after he left. Designed to erase in inventory tracking system, the bomb was discovered only by chance.
- Trojan horse: The Trojan house covertly places illegal, destructive instructions in the middle of a legitimate program, such as a computer game. Once you run the program, the Trojan horse goes to work, doing its damage while you are blissfully unaware. An example of a Trojan horse is Format C.
- Redlof: The Redlof virus is a polymorphic virus, written in Visual Basic Script .The virus relies on the Microsoft ActiveX component vulnerability to automatically execute itself. When executed the virus locates Folders.htt and infects that file, the Folder.htt is part of Microsoft Windows Active Desktop feature. It searches the users hard-drive and locate infectable files and appends itself to them.
- Some viruses may make unnoticeable changes hence corrupting the data being used and some viruses may even make data unusable.
- A virus program may detect some special information like passwords or any sensitive data and send it to some other user on network. For Example a virus program may read the Pin code or credit card number entered by a user and then send this information to another user.
- Another interesting thing a virus can do is that it may make resources unavailable to the users. For example, a virus after copying itself on all computers on a networks will start sending data on the network so that other users cannot use the network.
How To Safeguard against viruses?
Following are the few ways following which you can save your computers from getting infected by a virus. Never open unknown email messages, and also scan (for virus) all email messages even if you know the sender of the message. You should also minimize the data transfer between computer through the use of floppy disks and other removable media. While using the Internet, do not download free-ware programs without first checking it for virus.
Always use a virus detecting software i.e. Norton, McAfee, Dr Solomon’s, toolkit or IBM’s antivirus programs to detect and to delete the infected programs from your system. You should periodically update these versions of these programs more and more viruses are discovered over the time, so older way to save yourself from the destruction of viruses.
Another important way to save yourself from the destruction of viruses Attack is that you should always keep back up of your data. The backup will be useful if a virus attack deletes your data or modifies it.
