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What is a Virus ?
What is a Spyware ?
What is a Computer Worm ?
Antivirus Software
Vulnerability
Replication strategies
Recovery methods
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If there is anything a computer user wants to avoid, it is the latest computer virus. By understanding the basics behind virus replication, users can take steps to avoid contracting potentially damaging viruses.
Nonresident viruses:
Two conditions must be met before a virus can reproduce or replicate itself. First, it has to replicate code. Secondly, the code must be written to memory. Some viruses become parasites of sort; they attach themselves to executable files of legitimate programs. If this is the case, the virus’ code is put into effect.
Viruses come in two basic forms, nonresident viruses and resident viruses. A nonresident virus operates under a run-and-get-‘em mode. It contains a finder module that seeks out new files to infect. Once it is locked on target, the finder module signals the replication module to contaminate that file. A resident virus uses a parasite mode. It also contains a replication module that inserts into memory when it is executed. The replication module is signaled every time the operating system executes the appropriate file.
Resident viruses can be categorized as fast infectors or slow infectors. Fast infectors concentrate on contaminating as many files as possible. The more files that are infected, the better the chances are of discovering the virus. This method relies on sheer numbers to conquer the computer’s function. The contamination may slow the computer down or cause it to act suspiciously and catch the attention of anti-virus software. Slow infectors are created to infect files much less often. They tend not to slow down computer functions and often go unnoticed by anti-virus software. Slow infectors may only infect files when they are copied. They are not as successful as fast infectors are.
Viruses have specific hosts or transmission media. These include executable files; for example, COM files and EXE files in MS-DOS and Portable Executable files in Microsoft Windows. Master boot files are at risk for viruses. Microsoft Word and Excel files are vulnerable because they may contain macros. Macros are often a target host for a virus.
Viruses can avoid detections in several ways. They can overwrite areas of executable files and escape notice because the size of the file hasn’t changed. The most famous of these cavity viruses, as they are known, is the CIH or Chernobyl Virus. Anti-virus programs perform specific tasks; some viruses destroy these tasks before they can be executed and thus escape notice.
Virus replication strategies have become more complex over time. Windows is the most vulnerable operating system but no operating system is completely safe from a computer virus.
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