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Computer viruses
Tomáš Balíček | 08. listopadu 2008
Tomáš Balíček | 08. listopadu 2008
21a – Viruses
A computer viruses is a self-replicating code hidden in a computer programs and intended (má v úmyslu) to corrupd (narušit) a system or destroy stored data. It is usually a relatively simple inoptrusive (nenápadný) program, that works in different ways:
• Benign (neškodné) viruses, cause (způsobují) a messagge to pop up on the screen
• Masicious (zboubné) viruses, are able to simulate a fault (chyba) in the PC operation, to reman (zpřeházet) the PC keyboard or to erase or alterace (pozměnit) a databaze.
• Boot sector viruses infiltrate the boot sector of a disc.
• Files viruses attack them selves to executable files and device drivers or other computer parts can be attacked by other infections.
• Stealth (skryté) viruses access the system after having bypassed the DOS.
The number of viruses is increasing rapidly and they are changing their work habbits (návyky). There are numerous anti-viruses programs, which can protecte a PC system or eradicate (vyhubit) a virus in a variety of ways. Some of them can load a terminace-and-stay-resident (TRS) program in to the PC memory to continually watch for viral activities. There are numerous screening programs the recognize and destroy known viruses by scaning the fines stored on a disc bit-by-bit manner (metodou bit po bitu) and by comparing them with a library of known virus-infected files.
Some sophisticated (důmyslné) programs are able to watch for virus like activities by scaning the disc repeatedly and comparing the original data and the new checksums. Another method is to immunize files by adding a special code called integrity statistics to them so that the program acted like a checksum. In addition (navíc k) to software anti-virus countermeasure (protiopatření), there exit hardware options for detecting infections. One of them uses a special immunizer plug connected to the PC’s paralel port.