Nowadays, it seems that only a computer, disconnected from the World Wild Web may be safe enough from any kind of attacks by, so-called, Malware. For those innocent, who do not know yet what the 'Malware' stands for, here is a lightweight definition: the Malware is a type of a code that may cause a break or damage of your PC, or, in a broader sense of the word, any computer system or network.
As any study begins with terms and limits, it is worthy to start this one with a more precise disclosure of all main and known so far types of the Malware and a bit of history.
The very first beast had a name 'virus', which is a program that is unable to a self replication on a host computer but is effective when the user needs. The first generation of viruses marked this world in the early 80's, on the Apple II and, during last decade, their evolution keeps gyrating wildly. However, the pioneer in the PC family (DOS), called the Brain, emerged in 1986. After it, the world has seen such things like a polymorphic virus (1990) and the macro virus (1995). Each of them deserves a separate story.
The next spiral was named the Morris Internet Worm, by R. T. Morris Jr., in 1988, which affected most of the Internet of that time. Technically, a worm is recognized by its ability to replicate itself across the networks and, usually, without the user's help. The so-called malicious mobile code presents a bunch of scripting and non-scripting pieces, which may easily make a real mess of your computer in no time. A significant representative of the breed might be the StrangeBrew virus, as it was the first Java program (1998) that began the count of viruses for the web-applications. Notably, Java is not the only possible language to produce something of that kind, since the VBScript or ActiveX also make their contribution.
Next and very new by its nature is a row of administrative tools, like the VNC (Virtual Network Computing) or the Netcat, which are to attack a victim computer and it may be a real disaster. Being itself a very powerful tool to investigate a system security since the late 90's, it happened many times to be a tool to slip the security controls as well. Any of these are commonly known as 'Backdoor', the Trojan horse.
Here it is worthy to mention the Setiri (2002) and the Hydan (2003). The former can go through the personal firewall or the NAT (Network Address Translation service, which usually comes along with the firewalls), and the latter is capable to encapsulate the data inside the executables, which supply much more functionality that it may seem.
The RootKit is a kind of the Malware hi-tech, as they give a chance to modify the very self operating system, installed on your computer. Certainly, to do such things, the attacker must be very good in the kernel hacking and the network stack. The RootKit is a relatively young and it is enough to recall here the 'Knark Kernel-Level RootKit' (1999).
To summarize all the above said, the reader should note that every day hordes of the malware creators are inventing more and more sophisticated "chef-d'oeuvres" in order to attain something they do not want you to know. Stay in touch for more findings...