Economic importance of computer virus
To enable metamorphism, a "metamorphic engine" is needed. The virus will eventually be activated by the "trigger" which states which event will execute the virus, such as a date, the presence of another program or file, the capacity of the disk exceeding some limit or the user taking a certain action e.
While almost all Trojan horses attempt to cause harm to the computer system, more than 70 percent of all computer viruses and worms are designed only to self-replicate.
Metamorphic code[ edit ] To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. The term "polymorphic" means many-formed.
This technique enables the viruses to sneak past antivirus software because every time the antivirus program attempts to scan an infected file, the virus disinfects the file first. Secondary Attacks It is more difficult to quantify the cost of this type of attack.
Types of computer virus and definition each type
Social engineering and poor security practices[ edit ] In order to replicate itself, a virus must be permitted to execute code and write to memory. Viruses that utilize this technique are said to be in metamorphic code. Macro viruses spread through documents, spreadsheets, and other data files that contain computer macros. If program B is already infected, the virus goes back to locate another program to infect. Most often, Trojan horses either steal information such as passwords or files from the computer or damage the contents of the computer by deleting files. Some worms, like the Internet worm of , automatically connect to target computers and use a "back door" to install and run themselves on the target without human intervention. Boot sector viruses[ edit ] Email virus[ edit ] Email viruses are viruses that intentionally, rather than accidentally, uses the email system to spread. The Reaper program was created to delete Creeper. Many companies consider spyware the most serious threat. See polymorphic code for technical detail on how such engines operate.
They are always induced by people. It also includes loss of productivity, and consequently revenue, due to employees being unable to use the system, plus potential loss of company data from the system. The Trojan Horse Trojan horses are software programs that are designed to appear like normal computer programs, yet, when run, can cause some type of harm to the host computer.
Why is it important to know about computer viruses
Like viruses, computer worms can be written in assembly language, scripting languages, macro languages, or in high level languages like C, C, or Java. EXE or. The virus automatically disinfects infected files before they are accessed by other software on the computer, then reinfects them at a later time. Software development strategies that produce large numbers of "bugs" will generally also produce potential exploitable "holes" or "entrances" for the virus. The worm sends itself to each of the target computers. The first computer worms were written at Xerox Palo Alto Research Center in to understand how self-replicating logic could be leveraged in a corporation. A Short Course on Computer Viruses, 2nd edition. Resident viruses overwrite interrupt handling code or other functions , and when the operating system attempts to access the target file or disk sector, the virus code intercepts the request and redirects the control flow to the replication module, infecting the target. The Trojan Horse Trojan horses are software programs that are designed to appear like normal computer programs, yet, when run, can cause some type of harm to the host computer. The work of von Neumann was later published as the "Theory of self-reproducing automata".
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