Computer Virus
In 1983, Fred Cohen coined the term “virus”, postulating a virus was a “program, which he e ‘infect’ other programs by changing to include possibly evolved copy of itself. ” Period, the virus is actually a shortcut to the vital information resources under seize. Mr. Cohen extended his definition a year later in his 1984 paper, “virus “, commented that” the virus can spread throughout a computer & # x10D; the system or network by any authorized user via ; it to infect their programs. Every program that gets infected may also act as a virus infection, and therefore grows . Computer viruses, as we know it today, originated in 1986 with a Brain – the first virus for personal computers. Two brothers wrote (Basid and Farooq Alvi, who ran a small software důmv Lahore, Pakistan) and the & # x10D; al race between viruses and anti-virus programs that still continues today. & # XD; With the above explanation, we can say that viruses infikuj & # xED; program files. However, viruses can infect certain types of data files, especially those types of data files Back up & # xED, executable content, such as files created in Microsoft Office programs that rely makra.Zvyšovat difficulty of definition, there are viruses and demonstrate that a similar ability to infect data files that are not typically support executable content – for example, Adobe PDF files commonly used for shared & # xED, documents, a. JPG image file. However, in both cases the virus has a dependency on outside ; Heavy executable, so no virus can be considered more than a simple ‘proof of concept’. In other cases, data files themselves may not be infectable, but man e to allow the introduction of viral code. Specifically, it is possible vulnerability in some products allow data files to manipulate such , m in a way that it causes the host program to become unstable, which may be harmful for ; code be introduced into the system. These examples are given only to note that viruses no longer relegate themselves simply infecting program files, as in when Mr. Cohen first defined the concept. So, to simplify and modernize, can be safely stated that the virus infects other files, whether program or data. Computer viruses are just viruses because they share some traits of biological viruses. Virus passes from computer to beg & # xED; tac as a biological virus passes from person to člověka.Existují similarity at a deeper level as well. A biological virus is not alive. The virus is a fragment of DNA inside a protective shell. Unlike cells, the virus has no way to do something, or reproduce to itself – is alive. Instead, a biological virus must inject its DNA into the cell. Viral DNA then uses the cell to reproduce the existing plant & # xE1; m. In some cases, filling buněks new viral cha ; STIC to burst, releasing the virus. In other cases, new virus particles bud from the cell one at a time, and cell ka is still naživu.Akcie virus, some of these characters. Virus, back to the top of the other program or document that you executed. Once started, it is then able to infect other programs or documents. It is clear that the analogy between computer and biological viruses stretches things a bit, but There are similar enough that the name hole.Počítačový virus is a program that replicates. To do so, you must connect only to other program files (eg. Exe,. Com,. Dll ) and run whenever the host program runs. In addition to simple replication, the virus almost always tries to fulfill a purpose : škodu.Volal cause damage routine, or payload, m & # x16F, the destructive part of the virus ranged from overwriting important & # xE9; information stored on the hard disk partition table to encode whose sel in the tables to just taunting the user with sounds, images, or unpleasant vliv.Je good m & # xED; t remember the wall without the “damage routine, as viruses can be run, eat & # xED; woman then it will continue to proliferate – demanding of system memory ti, disk space, slowing network traffic and generally deteriorating performance. In addition, the virus code is often buggy and can be a source of mysterious system problems that weeks to understand. Yes it can, whether the virus is malicious or not, his presence in the system lead to instability and should not be tolerována.Některé viruses in conjunction with “logic bombs,” don ‘t make & # xED; their presence known moons. Instead, the damage immediately, these viruses do nothing but repeat – the preordained release date or event when the damage unleashed their routines on the host system or the entire network & # x11B;. The impact of computer viruses to reprogram systémůVirus can do many kind of & # x16F, including damage následujících.1. Copy to other programs or areas disku.2. Replicate, how fast and often as possible, fill the infected system disk and system memory, rendering & # x16F k ničemu.3. View information on obrazovce.4. Changed, damaged or destroyed souborů.5 selected. Delete the entire content disku.6. Fallow for a specified period or until the condition is met, and then becomes aktivní.7. Open the rear dveřes infected system that allows someone else cess ; access and even control the system via a network or connected & # xED k internetu.8. Some viruses can cause system crashes, some programs (typically Windows) to behave podivně.Jak viruses & # x161, Iri from one system to another? most likely my hundred virus entry into the e-mail, Internet and network connections, floppy disk drives, and modems or other serial # & xE9, or parallel port connection. In today’s increasingly interconnected workstations (Internet, intranet, shared & # xE9; disks, removable disks, and e-mail), viral epidemics can spread more quickly and with ; IRSI than ever předtím.Níže are some go , not the ways the virus to enter the computer users’ system: • E-mail & # xE9; Annex • malicious scripts on web pages or HTML e-mail • ; FTP traffic from the Internet (download) • A shared network files and network ; ový operation in general • • Demonstration of software pirated software • Shrink- packaging, production programs (rare) • Computer & Laboratory # x159; ies • Electronic bulletin boards (BBS) • floppy disk swapping ; (using a floppy disk for transporting other people’s data and programs back and forth) High risk souboryNejnebezpečnějš ; more file types are:. Exe,. Com,. Xls,. DOC,. MDBVzhledem that do not need any special conversion infect computers & # x10D – everything I do is run, and because the virus spreads. It was estimated that 99% of all viruses are written for these formats souborů.Seznam potential virus carriers includes: EXE – (executable file) SYS – (executable file) COM – (executable file) DOC – (Microsoft Word), XLS – (Microsoft Excel), MDB – (Microsoft Access) ZIP – ( compressed file, common in the USA) ARJ – (compressed file, common in the U.S.) DRV – (drivers shine ; management) BIN – (Shared boot sector image file) SCR – (Microsoft screen saver) Common Pr & # xED; signs of viral infection computer will not start. computer hard & # xE9; m disk is reduced. applications will not load. application takes ; more load than usual period. Hard diving activity with increasing & # x161; uje especially when nothing is being done on the computer. antivirus software to see & # xED; report. amount of hard drive for bad sectors is increasing. Unusual graphics or messages displayed on screen files missing (deleted) report shows the hard disk can not detect or recognize. strange noises coming from beg & # xED; tion. Some viruses take control of the keyboard and occasionally replace the adjacent # & xED; indeed one key pressed. Another virus ’swallows’ keystrokes, so nothing appears on the screen. Interesting are the effects of system time. Hours will be back are particularly frightening for workers who can not wait until you go home. More seriously, this type of virus can cause chaos to the programs that are dependent & # xE9, the system time or date. Some viruses can become expensive option for users of the modem. We do not know, the one that dials a premium phone numbers, but no doubt will see me one soon. Jednímz particularly dangerous virus, dial 911 (the number of thousand & # x148; s lines in the U.S.) and takes up precious time in rescue služeb.Kategorie viruses Depending on the source of various types of viruses can be divided as follows zp & # x16F; manner: VIRYZvyšující PDA PDA, the performance has spawned a new kind of viruses. Wickedly creative programmers leveraged PDA the ability to communicate with others shine & # xED; ment and run programs that wreak havoc digitální.Blaženě safe his world, where users of these devices could synchronize and download impunity ended in August 2000 with the discovery of the virus Palm Liberty. Since then, many other viruses have been objeveny.Ačkoli is not yet as harmful as their PC- based cousins, these viruses still pose a threat to unsuspecting users. Their effects vary from harmless flicker side Flash & # xE1; you or an increase in energy consumption, to remove all the installed programs. But the threat is growing, and the destructiveness of these viruses are expected to parallel the development of facilities ; tion that útok.Vícestranné VIRYVirus, which combines two or more different methods of infection called multilateral virus. This type of virus can infect files and boot sector of the disk. Multi-split viruses have some characteristics of boot sector viruses and file viruses : They can get infected. com files. exe files and boot sector of your hard disk. The computer is booted up with an infected floppy disk is a typical multi-split virus first live alone in mind you can then infect the boot sector of your hard disk. From there, the virus can infect PCs around the environment. Not many forms of this virus class actually exist. However, they do form a disproportionately large percentage of all infections & # xED;. Tequila and Anticad are examples of distributed virů.PUMYNejvíce prevalent types of bombs are timed ; bombs and logic bombs. Hidden time bomb in the victim’s disk, and waits until a certain date, P & # x159; before running it. Logic bomb can be activated by changes in the data file, or concrete steps taken by the user or program. Bombs are considered viruses because they can cause damage or disruption in systému.Viry sektoruAž startup to mid 1990 -, boot sector viruses were most widely řenější virus, spread mainly in the 16-bit DOS world & # x11B, via floppy disk. Boot sector viruses infect the boot sector on floppy disk and spread the user to the hard disk, and a man e also infect the master boot record (MBR) on the user’s hard drive. Once the MBR or boot sector on the hard disk is infected, the virus tries to infect the boot sector of every disk that & # xE1, is inserted into computers and access. Examples of boot sector viruses are Michelangelo, Satria and Keydrop.Viry Boot sector work like this: Suppose that a user receives an infected floppy disk boot sector. The user copies the data from it, but forgot to remove it from the drive A:. When he began to download or run the next time the computer & # xED; infected the boot sector program from a floppy disk. Virus load first and infect the hard drive. Note that this can be prevented by w e changing the boot sequence in CMOS (Flight C: drive boot before A:). By hiding in the first sector on the disk, the virus is loaded into memory before the system & # xE9; files are loaded. This allows it to take complete control of DOS and interrupt the process of replacing the original content of the MBR or DOS boot sector with its own content and move the original boot sector data to another area on the disk. Given that the virus has infected the system on the hard disk will be loaded into memory each time it is computer is started. This will initially take over the lowest level of service to drive the system before running the original boot sector code, which is stored in another C & # xE1; sti hard drive. It seems that computer behave exactly as it should. Nobody will notice a few extra fractions of seconds added to the deployment sekvence.Při norm & # xE1; lním traffic virus will happily remain in memory. Because the disk check services that are easy to follow application access to disk – including floppy disks. Once it gets a request for access to a floppy disk, which provides that the disk is in the floppy drive. It will then assess its boot sector that has already been infected. If you find a floppy disk, clean it replace the boot sector with its own code. From this moment on the disk will be “carriers” and became a medium for the infection to other PC.Virus will also watch a special drive from & # xE1; enough to access the boot sector. Contains its own boot sector code, and the requirement for reading it could býtz anti-virus program checks for the presence of viruses. The virus does not read the boot sector and will redirect all requests for space hard disk on which is supported by the original content. In this respect, nothing unusual is detected. Such methods are called stealth technology and its main objective is to mask the presence of the virus. Not all boot viruses use stealth, but those společné.Boot viruses infect non-file (system ) and the hard disk. These areas offer an effective way of spreading the virus from one computer e to another. Boot viruses achieved higher success rate than viruses contesting the program & # xED, its objectives and can a virus šíření.Zaváděcí e infect DOS, Windows 3 x, Windows 95/98, Windows NT, and even Novell Netware systems. This is because the use of natural features of your computer (and not operational tion System), disseminate and aktivovat.Vyčištění boot sector virus, God can ; that be done by introducing the machine from an uninfected floppy system disk rather than from the hard disk, or that finding the original boot sector and replacing it in the correct location to disku.CLUSTER VIRYTento type virus will change the file system disks. If you run the program from an infected disk, the virus causes the program to run well. This technique creates the illusion that the virus has infected every program disk.E viryTyto-mail viruses can b & # XFD; t transmitted via e-mail messages sent via private & # xED; networks and the Internet. Some email viruses are transmitted as an infected attachment, the document file or a program that is added to the report. This type of virus is triggered when the victim opens the file that is attached to the message & # x11B;. Other types of viruses reside in the body of the message itself. To store the virus, the report must be encoded in HTML format. After having launched a number of email viruses attempt to spread the sending messages to everyone in the victim’s address book, each of these contains a copy of viru.Poslední & # x11B c, which in the world of computer viruses, e-mail virus called Melissa virus, that surfaced in March 1999. Melissa spread in Microsoft Word documents sent by e-mail, and it worked like this: Someone created the virus as a Word document uploaded to the Internet newsgroup. Anyone who downloaded the document and open it would cause a virus. The virus would then send the document (and therefore itself) in an e-mail message to the first 50 people in personal contact. E-mail message contains a friendly note that included name of the recipient would open the document thinking it was harmless. The virus would then create 50 new zprávz recipient machine. Consequently, the Melissa virus was the fastest-spreading virus ever seen, and forced several large companies shut down their e-mail systems in the době.Virus ILOVEYOU, which occurred at 4 . May 2000 was even easier. It contained a piece of code as attachment. People who double clicks on the attachment allowed the code to execute. Code sent copies of itself to everyone in the victim’s Address Book and then started corrupting files on the victim machine. It is as simple as a virus can get. This is really more of a Trojan horse distributed by e-mail before it is used virus.Virus Melissa programming language built into Microsoft Word called VBA, or Visual Basic for Applications. It is a complete programming language and can be programmed to do things like me thread files and send e-mail messages. It is also useful but dangerous auto-launch feature. A programmer can insert a program into a document that runs instantly whenever it is open & # x159; en document. This is how the Melissa virus was programmed. Anyone who opened a document infected with Melissa would immediately activate the virus. It would send the 50 e-mails, and then infect a central file called NORMAL. DOT so that any file saved later would also contain a virus! That created a huge nepořádek.OBRÁZEK infikováníSoubor harmful viruses involved in memory & # x11B, and they usually infect executable files with the following extensions: *. COM, *. Exe, *. DRV, *. Dll, *. BIN, *. CTRL, *. SYS. They activate every time the infected file is executed by copying themselves into other executable files and may remain in memory long after the virus to infect different sets aktivován.Tisíce ; her viruses exist, but similar to a boot-sector viruses, carried by passengers & # x17E, on the majority of work in 16-bit DOS environment. Some, however, successfully infected Microsoft Windows, IBM OS / 2, and Apple Macintosh prostředí.Soubor viruses can be further separated into categories ; sub-incidentally, that manipulate their targets: TSR FILE VIRYMéně common type of virus is close -and-stay-resident file virus. As the name suggests they infect files usually are. com a. exe files. There are however some viruses device drivers, some viruses ; infect overlay files, namely over 99% of the executables have a. com a. exe, some not. TSR for the virus to spread someone has to run an infected program. The virus is usually memory resident looks at each program starts and then it infects. Examples of file viruses are TSR Dark Avenger and Green Caterpillar.Přepisování VIRYTyto viruses infect cess epsáním part of their target with its own code, but, w ek file corruption. The file will never serve any purpose other than spreading the virus Next & # xED;. For this reason, they are usually found quickly and easily without šířit.Parazitární VIRYTyto viruses themselves cess ; Connect to executable files without substantially changing the content of the host program. They attach to the addition of their code at the beginning, end or even in the middle & # x159; ed file and redirect program flow so that the virus is executed first. When the virus has finalized its work, control is transferred to the host. Execution host is a bit late, but this is usually not older applications patrný.MakroviryMnoho me l simple macro systems, which allowed the user to record a sequence of operations in the context of & # xE1, fairly and associate them with specific keys. Later, the user would perform the same sequence of events intended to press only klávesy.Novějš s applications provide a more complex macro systems. The user can write the whole macro-programs that run in a word processor or spreadsheet , m and the environment is directly connected to word processing and spreadsheet files. Unfortunately, this capability also allows you to create macro viruses viry.Macro currently is & # xED, about 80 percent of all viruses, according to the International Computer Security Association (ICSA), and are the fastest growing viruses in computer history e. Unlike other viruses, macro viruses are not specific to the operating system, you & # x159; it is easy to use e-mail attachments, floppy disks, Web downloads, file transfers, and Cooperative aplikace.Makro viruses are, however, application-specific. A macro virus is designed to infect a file type of document such as Word or Microsoft Excel. They infect macro tools that accompany such applications as Microsoft Word and Excel, which means Word macro virus can not attack Excel document and vice versa. A macro virus is embedded in the document file and can travel between data files in Excel and can potentially infect hundreds of files, if discouraged by this process into different levels of damage data from corrupt documents lubrication dat.Makro viruses are written “Every man is a programming language – Visual Basic – and are relatively easy to create ; it. They can infect at different points in the set used, for example, when he opened saved, closed, or vypouštíTypický chronology of macro virus infection begins when & # x17E, is loaded with an infected document or spreadsheet. The application also loads that accompany macros, which are attached to the file.