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A virus is a hidden element that lurks in a system until activated. For humans, that system is the human body, and the activated element can be as ordinary as the common cold. For PCs, that system is a computer, and the activated element is a virus affects otherwise normal software programs and systems. And it can be deadly.
When a virus infects a computer, the viral code replicates itself and spreads quickly, infecting more and more as it grows. Every time a user saves an infected program to a floppy disk, the virus gets saved also. Whenever that disk is loaded onto a new PC, the virus gets loaded too. When that PC connects to a network server, the virus connects too. Since most viruses remain hidden, most users have no idea that they are passing around a deadly poison until it is too late.
The most common computer virus acts as a string of code that attaches itself to a normal software program, often affixing itself to file extensions that end in .EXE or .COM. All computer programs are made up of thousands and thousands of lines of software code, the actual language that creates the program. The string of the viral code hides itself amongst the normal code. Once infected, software programs frequently change in size as the virus adds code to the beginning or end of the program. The most common computer viruses range in size of between 2000 and 4000 bytes of code.
Is there more than one type of computer virus?
Most computer viruses fall into one of two categories - benign or malignant. Although benign viruses quickly replicate, they tend not to corrupt data or attempt to do anything more previous than display annoying messages on the screen or frequently slow down your system. However, malignant viruses replicate very quickly with the intention of causing great harm to data stored on floppy disks or a computer's hard drive. The sole intention of most malignant viruses is to destroy as much data as possible in a very short period of time.
Both benign and malignant viruses can be either boot sector viruses or file viruses. The boot sector is the portion of the disk reserved for the self-starting portion of a program. Boot sector viruses infect both the boot sectors of a floppy disk as well as a computer hard drive. If a floppy disk with a boot sector virus is inserted into a PC's floppy disk drive (generally the A or B drive of a computer), the virus loads itself into memory and replaces the hard drive's boot sector with its own infected code. Each time the PC is turned on, the virus loads itself into memory and waits to infect and floppy disks inserted into the disk drives.
With file viruses, the virus attaches itself to an executable program file and loads itself into memory, searching for other executable files to infect. The deadly similarity between a boot sector virus and a virus is that they both remain in a computer's memory and can infect any new files copied onto the hard drive or inserted as a floppy disk into the computer system.
All computer systems can be exposed to viruses. Computer viruses can infect any form of write-able storage medium - including hard disks, floppy disks, tapes, CD-ROMs, optical media and all forms of memory.
How quickly can a virus infect my computer system?
With a single user, a virus can make dozens of perfect, identical copies of itself within minutes of infection. Once a PC is hooked up to a computer network system, that same virus can infect every other PC in am office environment in a very short period of time. Networks themselves do not necessarily become infected; instead, they may act as carriers of the virus, infecting all PCs currently hooked up to the network system, as well as those that eventually logon.
Simply put, computer viruses are extremely damaging both to businesses and individual users.
A recent survey showed that in North American corporations with more that 400 PCs, over 50% of the companies had experienced a virus attack. The study also found that the rate of corporate PCs infected with a virus is increasing at an alarming rate, with 26% of all sites discovering an infection in a single month.
In another study, more than 9% of the companies interviewed said they had experienced "disastrous" data losses due to computer viruses. It is estimated that in the U.S. alone, computer viruses cost businesses over $1 billion dollars in lost profits ever year.
Although the examples above all pertain to North America, the rest of the world is not immune. Computer viruses have been reported in well over 100 countries around the world, reaching every continent on the globe.
What happens when a virus infects my system?
When a virus attack occurs, the most common setbacks are:
The most common setbacks to your work or business include:
Once data is lost, it cannot be recreated. Instead, most companies find themselves in the position of having to recreate files, programs and business records. In addition, company morale usually suffers not only because the victims blame themselves for infecting the computer system, but also because the company must waste resources to recreate work that has been destroyed.
Is it expensive to have a virus removed from my computer system?
It can be very expensive. Although some viruses can be removed with minimal effort or loss of productivity, other viruses can be very difficult to eliminate. This is especially true of computer systems hooked up to a network server which requires that every PC accessing that server be checked for possible infection.
In addition, once a computer virus has been eliminated there are no guarantees that the company, or computer is virus-proof. Statistics show that 90% of all victims who clean out their systems find that they are re-infected within 30 days. This can occur from some undetected copy of the original virus lurking in the system or from an outside source, perhaps the same source that infected the system the first time.
How many computer viruses are there?
In 1986 the National Computer Security Association (NCSA) estimated that there were four known computer viruses. Today there are over 46,924 known computer viruses, with an average of 110 new viruses discovered each month.
While the number of viruses is increasing, consumers are seemingly unaware. NCSA estimate that 35 out of every 1000 PC's are hit by a virus each month. This means that over the course of a year, a user has almost a 50% chance of being infected by a virus. However, only 40% of the PC owners have an installed anti-virus product.
Will an anti-virus program protect me from being infected?
Unfortunately, no. Virus scanning programs, although helpful in detecting some known viruses, are only as good as their database of common viruses they search for. With the rapid development of new viruses, estimated to be over 110 new viruses per month, virus scanning programs are not able to detect most of the new viruses until it is too late.