Computer Virus and Its Prevention Methods

4916 WordsApr 2, 201320 Pages
LETTER OF TRANSMITTAL Chapter one Computer virus COMPUTER VIRUS A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly, but erroneously, used to refer to other types of malware, including but not limited to adware and spyware programs that do not have a reproductive ability. Malware includes computer viruses, computer worms, ransomware, Trojan horses, keyloggers, most rootkits, spyware, dishonest adware, malicious BHOs and other malicious software. The majority of active malware threats are usually trojans or worms rather than viruses. Malware such as trojan horses and worms is sometimes confused with viruses, which are…show more content…
They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example, the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file. Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them. As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access. Read request intercepts While some antivirus software employ various techniques to counter stealth mechanisms, once the infection occurs any recourse to clean the system is unreliable. In Microsoft Windows operating systems, the NTFS file system is proprietary. Direct access to files without using the Windows OS is undocumented. This leaves antivirus software little alternative but to send a read request to Windows OS files that handle such requests. Some viruses trick antivirus software by intercepting its requests to the OS. A virus can hide itself by intercepting the request to read the infected file, handling the request itself, and return an uninfected version of the file to the antivirus software. The interception can occur by code injection of
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