Computer viruses are programs similar to biological viruses spread after getting into unexpected action a computer do. Although all viruses are not dangerous, but many of them aimed at the destruction of certain types of files, applications or operating systems are written. Similar viruses all programs other system resources such as memory and disk space, CPU and other resources can take advantage and can do dangerous actions eg files on disk and delete or entire hard drive their format. Also, a virus can permit access to the device through the network without authentication provided. For the first time in 1984 the word "virus" means the person by Cohen in academic texts were used. In this article, that "experiments with computer viruses" was the name of a particular author or category of programs known as viruses and named the Leonard Dlmn is attributed.
However, before this time, viruses in the context of practical and imaginative stories were appearing. Viruses boot sector: boot sector first Sector on floppy or hard disk computer. Executable code stored in the sector have been using their computer activities are performed. Considering that every time the computer Rise Boot sector about referral is placed, and with every computer configuration changes also re-boot sector content is written, so this sector very vulnerable place against virus attacks is. This type of virus through infected floppy disk boot sector that they are published. Boot sector computer hard drive that is infected by the virus and every time the computer is turned on, the virus load in your memory and wait for the opportunity to infect floppy stays in order to publish your device and another to pollute. These viruses can act that way until the machine is infected computer can boot from hard disk to be wiped out. Virus after writing on the original source code to try to boot to another sector on disk and transferred to the sector as a bad sector (Bad Sector) to Mark. Macro viruses: these viruses directly infect programs do not. The aim of these viruses, files produced by programs that Makrvyy programming languages such as Exel or Word documents to use. Macro viruses through the disk, network or file attachments by e-mail is to be expanded. Viruses can activate only when the infected file is opened, the virus then began to expand its computer and other files available will also infected.
Transfer these files to other computers or share files between different devices cause pollution to the spread of viruses is. File infecting viruses: executable files (files ending in. Exe and. Com) and simultaneously infected with the implementation of these programs on your memory and start to spread and infect other executable files system must . Some examples of this virus in your text rather than text to the executable file. Chndrykht viruses (Polymorphic): This virus infected file in any way appear. Note that the encryption algorithms used to detect and clean to detect and identify these viruses is difficult. Virus secret: The virus try your operating system and antivirus software to keep secret. For this virus in living memory and retaining access to the operating system is. In this case, all requests that virus anti-virus software to the operating system to be awarded. Thus, anti-virus software also cheated and there is the notion that any computer virus does not exist. The most common types of viruses Chndbkhshy this combination of viruses boot sector viruses and file infecting is. The combination of other types of viruses is possible.
Other malicious programs, some scholars Trojan horses, worms and logic bombs in the category of viruses do not, but the fact is that these programs also can be very dangerous and serious damage to computer systems must enter. Trojan horses pretend Knndkh do something special, but in practice have been made for another purpose, for example, a program that pretends to be a game but actually allow remote access to a computer user provides said. Worms are programs similar to viruses that can multiply their own, usually cream vulnerabilities in the e-mail program for fast and wide distribution of their world are. Logic bombs are programs that in some predetermined time, such a special day; do unexpected things.
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