1. Overwriting file viruses have a limitation. What is it? 2. Despite limitation
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Question
1. Overwriting file viruses have a limitation. What is it?
2. Despite limitations, overwriting file viruses has a benefit. What is it?
3. What are boot viruses?
4. How do boot viruses infect a machine?
5. Describe how an appending virus might infect a file?
6. What is a cavity virus? What is the advantage of this technique?
7. Commander Bomber had a novel infection strategy. What was it?
8. What is the purpose of entry point obfuscation?
9. What is polymorphism with respect to viruses?
10. When I talk about “encrypted” viruses, I’d say they are not really encrypted. What do I mean by that?
Explanation / Answer
1. Overwriting viruses is defined as viruses that replace or change the contents of other files with their own code.The content of an infected file is destroyed. A PC hit by an overwriting virus quickly becomes
unusable. Overwriting viruses is one of the most destructive viruses among all others.Many consider overwriting viruses to be extremely dangerous and harmful because they actually destroy elements
of a user's system or PC.
3. The boot sector is the 1st programming loaded onto your system or PC .This program lives in on a disk, this disk can be the hard disk inside the PC or a floppy disk or a CD. When a PC is set to on, the hardware automatically locates and runs the boot sector program. This program then loads the rest of the operating system into memory. Without a boot sector, a PC cannot programming or software.
4. A boot sector virus infects PC by modifying the contents of the boot sector program. It replaces the valid contents with its own infected version. A boot sector virus can only infect a machine if it is used to boot up your PC, for example, if you start your PC by using a floppy disk with an infected boot sector, your PC is likely to be infected. A boot sector cannot infect a PC if it is introduced after the machine is running the operating system.
. 6.Cavity VirusesA cavity virus tries to install itself inside of the file it is infecting. which is difficult.
Most of the viruses take the east and simple way out when infecting files; they simply attach themselves to the end of the file , then change the start of the program so that it 1st points to the virus and then to the actual programming code. Many viruses that do this also implement some stealth techniques so you don't
see the increase in file length when the virus is active in memory.
A cavity virus, on the other hand, tries to be clever. Some program files, for a various of reasons,have empty/clear space inside of them. This empty space can be utilized to house virus code. A cavity virus
tryout to install itself in this empty space while not damaging the actual program itself.
An advantage of the virus is that it does not increase the length of the program and can avoid the need for some stealth techniques. The Lehigh virus was an early e.g. of a cavity virus.
Because it difficult to write this type of virus and the limited number of possible hosts, cavity viruses are rare
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