HISTORY OF COMPUTER VIRUS PART 2

Vulnerabilities allow many different types of actions to be carried out. For example, they allow viruses to be dropped on computers directly from the Internet -such as the Blaster worm-. In fact, the effects of the virus depend on the vulnerability that the virus author tries to exploit.


In the early days of computers, there were relatively few PCs likely to contain "sensitive" information, such as credit card numbers or other financial data, and these were generally limited to large companies that had already incorporated computers into working processes.

In any event, information stored in computers was not likely to be compromised, unless the computer was connected to a network through which the information could be transmitted. Of course, there were exceptions to this and there were cases in which hackers perpetrated frauds using data stored in IT systems. However, this was achieved through typical hacking activities, with no viruses involved.

The advent of the Internet however caused virus creators to change their objectives, and, from that moment on, they tried to infect as many computers as possible in the shortest time. Also, the introduction of Internet services -like e-banking or online shopping- brought in another change. Some virus creators started writing malicious codes not to infect computers, but, to steal confidential data associated to those services. Evidently, to achieve this, they needed viruses that could infect many computers silently.

Their malicious labor was finally rewarded with the appearance, in 1986, of a new breed of malicious code generically called "Trojan Horse", or simply "Trojan". This first Trojan was called PC-Write and tried to pass itself off as the shareware version of a text processor. When run, the Trojan displayed a functional text processor on screen. The problem was that, while the user wrote, PC-Write deleted and corrupted files on the computers' hard disk.

After PC-Write, this type of malicious code evolved very quickly to reach the stage of present-day Trojans. Today, many of the people who design Trojans to steal data cannot be considered virus writers but simply thieves who, instead of using blowtorches or dynamite have turned to viruses to commit their crimes. Ldpinch.W or the Bancos or Tolger families of Trojans are examples of this.


Even though none of them can be left aside, some particular fields of computer science have played a more determinant role than others with regard to the evolution of viruses. One of the most influential fields has been the development of programming languages.

These languages are basically a means of communication with computers in order to tell them what to do. Even though each of them has its own specific development and formulation rules, computers in fact understand only one language called "machine code".

Programming languages act as an interpreter between the programmer and the computer. Obviously, the more directly you can communicate with the computer, the better it will understand you, and more complex actions you can ask it to perform.

According to this, programming languages can be divided into "low and high level" languages, depending on whether their syntax is more understandable for programmers or for computers. A "high level" language uses expressions that are easily understandable for most programmers, but not so much for computers. Visual Basic and C are good examples of this type of language.

On the contrary, expressions used by "low level" languages are closer to machine code, but are very difficult to understand for someone who has not been involved in the programming process. One of the most powerful, most widely used examples of this type of language is "assembler".

In order to explain the use of programming languages through virus history, it is necessary to refer to hardware evolution. It is not difficult to understand that an old 8-bit processor does not have the power of modern 64-bit processors, and this of course, has had an impact on the programming languages used.

In this and the next installments of this series, we will look at the different programming languages used by virus creators through computer history:

- Virus antecessors: Core Wars
As was already explained in the first chapter of this series, a group of programs called Core Wars, developed by engineers at an important telecommunications company, are considered the antecessors of current-day viruses. Computer science was still in the early stages and programming languages had hardly developed. For this reason, authors of these proto-viruses used a language that was almost equal to machine code to program them.

Curiously enough, it seems that one of the Core Wars programmers was Robert Thomas Morris, whose son programmed -years later- the "Morris worm". This malicious code became extraordinarily famous since it managed to infect 6,000 computers, an impressive figure for 1988.


- The new gurus of the 8-bits and the assembler language.

The names Altair, IMSAI and Apple in USA and Sinclair, Atari and Commodore in Europe, bring memories of times gone by, when a new generation of computer enthusiasts "fought" to establish their place in the programming world. To be the best, programmers needed to have profound knowledge of machine code and assembler, as interpreters of high-level languages used too much run time. BASIC, for example, was a relatively easy to learn language which allowed users to develop programs simply and quickly. It had however, many limitations.

This caused the appearance of two groups of programmers: those who used assembler and those who turned to high-level languages (BASIC and PASCAL, mainly).

Computer aficionados of the time enjoyed themselves more by programming useful software than malware. However, 1981 saw the birth of what can be considered the first 8-bit virus. Its name was "Elk Cloner", and was programmed in machine code. This virus could infect Apple II systems and displayed a message when it infected a computer.



Computer viruses evolve in much the same way as in other areas of IT. Two of the most important factors in understanding how viruses have reached their current level are the development of programming languages and the appearance of increasingly powerful hardware.

In 1981, almost at the same time as Elk Kloner (the first virus for 8-bit processors) made its appearance, a new operating system was growing in popularity. Its full name was Microsoft Disk Operating System, although computer buffs throughout the world would soon refer to it simply as DOS.

DOS viruses
The development of MS DOS systems occurred in parallel to the appearance of new, more powerful hardware. Personal computers were gradually establishing themselves as tools that people could use in their everyday lives, and the result was that the number of PCs users grew substantially. Perhaps inevitably, more users also started creating viruses. Gradually, we witnessed the appearance of the first viruses and Trojans for DOS, written in assembler language and demonstrating a degree of skill on the part of their authors.

Far less programmers know assembler language than are familiar with high-level languages that are far easier to learn. Malicious code written in Fortran, Basic, Cobol, C or Pascal soon began to appear. The last two languages, which are well established and very powerful, are the most widely used, particularly in their TurboC and Turbo Pascal versions. This ultimately led to the appearance of "virus families": that is, viruses that are followed by a vast number of related viruses which are slightly modified forms of the original code.

Other users took the less "artistic" approach of creating destructive viruses that did not require any great knowledge of programming. As a result, batch processing file viruses or BAT viruses began to appear.


Win16 viruses
The development of 16-bit processors led to a new era in computing. The first consequence was the birth of Windows, which, at the time, was just an application to make it easier to handle DOS using a graphic interface.

The structure of Windows 3.xx files is rather difficult to understand, and the assembler language code is very complicated, as a result of which few programmers initially attempted to develop viruses for this platform. But this problem was soon solved thanks to the development of programming tools for high-level languages, above all Visual Basic. This application is so effective that many virus creators adopted it as their "daily working tool". This meant that writing a virus had become a very straightforward task, and viruses soon appeared in their hundreds. This development was accompanied by the appearance of the first Trojans able to steal passwords. As a result, more than 500 variants of the AOL Trojan family -designed to steal personal information from infected computers- were identified.



Source:
http://www.antivirusworld.com/articles/history-6.php