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Sobota, 23. novembra 2024
What is a computer virus
Dátum pridania: 30.11.2002 Oznámkuj: 12345
Autor referátu: stiby
 
Jazyk: Angličtina Počet slov: 2 480
Referát vhodný pre: Stredná odborná škola Počet A4: 7.5
Priemerná známka: 2.97 Rýchle čítanie: 12m 30s
Pomalé čítanie: 18m 45s
 

Therefore there is no exactly defined law according to which "good" files may be told from "viruses". And more than that, for each particular file sometimes it is rather difficult to tell, whether it is a virus or not.
Here are two examples: KOH virus and ALREADY.COM program.
Example 1. There is a virus(?) utility(?) called KOH. This program encrypts/decrypts disks on a user request only. This is a bootable diskette with KOH bootstrap loader, somewhere in the other sectors there is executable code of KOH. After diskette boot up KOH asks user something like, "May I install myself to your HDD?" (if it already has been installed onto the HDD it asks the same about diskette). If the answer is yes, KOH transfers itself from one disk to another.
As a result KOH transfers (copies) itself from diskettes to hard drives and vice versa, but only if user permits to do so.
Then KOH outputs some text about its hot keys by pressing which it encrypts/decrypts disks - prompts for password, reads sectors, encrypts them and makes them unavailable if you enter incorrect password. By the way it also has a key for uninstallation, which is used by KOH to remove itself from disks (having decrypted all the encrypted data first, of course).
So KOH is a utility program for information protection from nonapproved access. However it has one additional feature: this program can copy itself from one disk to another (with user's permission). Is this a virus? Yes or no? Most likely not...
This might be okay, nobody would call this utility program KOH a virus, if it wasn't for one thing. The KOH's bootstrap loader looks 100 percent like that rather "popular" "Havoc" virus ("StealthBoot").. end of story. It's a virus! It even has an official name - "StealthBoot.KOH".
Had KOH been written by somebody in Symantec or Sierra or even by Microsoft and not by somebody unknown, nobody would even think of calling it a virus.
Example 2. There is a program called ALREADY.COM, which copies itself to different subdirectories on a drive depending on system date. Is this a virus? Yes of course - a typical worm virus, spreading itself over the drives (including the network ones). Yes?.. Yes!
"Close but no cigar!" As it turned out, this is not the virus, this is a part of some software. However if you detached this part from the rest of the software, it behaves like a typical virus.
So we have to live examples:
1. Non-virus - virus.
2. Virus - non-virus.
And attended reader who is no stranger to arguments may object:
- Hold it.
 
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