Systems Architecture Study Set 1
Quiz 11 :
Buffer overflows and Data Execution Prevention (DEP) Viruses and various other malware exploit the bugs which are known as the buffer overflows in the widely used software's. Thus, one of the methods that prevents these types of errors and exploits in the various software currently used in the Windows Versions is the Data Execution Prevention or DEP method. Buffer overflows is a type of overflow or it is a situation that occurs with the computer programs where a certain amount of the space that is allocated to store the data for the various programs during the execution occurs. Thus, if too much of the data is feeded or is given in input into the fixed amount of the space then such a space is known as the buffer and it will overflow thus, such type of overflow is known as the buffer overflow. Buffer overflow situation or also called as buffer overrun condition occurs when the program allows the input that is to be written beyond end of a buffer allocated. Buffer overflows is all about the memory that is if the memory is protected then the buffer overflows would not take place and the overflow that will occur would be due to some past situations. Data Execution Prevention or DEP is basically a protection mechanism.DEP is intended in order to prevent the applications from being executing the code in the non-executable regions of the memory and from the situation of the buffer overflow attacks that prevents the execution of the code on the heap or the stack. DEP is basically a Windows terminology that was introduced first in the Service Pack 2 of Windows XP and is basically included in 2005 Windows XP Tablet PC Edition. DEP or Data Execution Prevention prevents the malicious attacks via the buffer overflows as DEP is basically intended so as to stop the program, such as the worm and thus holds in the first place using the network attack. Thus these types of attacks often work by the technique called as the 'buffer overflow' which could cause the malicious data, supplied by worms to be executed. Thus this is caught by the DEP, and the program thus shutdown thus without allowing most of the infection in the process to complete. When the DEP triggers an infection that is usually headed off then the DEP do not deals with any of the existing infections and nor does it prevents the viruses. While another defense mechanism that is being implemented is called as the DEP, which stands for the Data Execution Prevention and is an attempt so as to prevent the return address from being altered into something in same memory space as the data, and thus also prevents machine code from being placed into the data segments. The return oriented programming (ROP) is thus used to defeat the modern DEP. Yes the method is always effective as it helps to prevent the computer from executing the code in the memory of data pages. While in most of the cases, the code is not usually executed from the default heap and from the stack. The hardware-enforced DEP thus detects code that is running from the given locations and thus raises an exception when such type of the execution occurs. The software-enforced DEP thus supplements the hardware Data Execution Prevention by preventing the malicious code from taking lot of the advantage of handling exception mechanisms in the Windows. A user or an administrator disables the DEP or Data execution prevention method because when a DEP is presented in front of the user then it alters a problem in front of them thus the message generated prevents the DEP problem that is occurred with the application and thus helps the user to learn more about the DEP and thus disables the DEP for the application that was being closed.
Function of each layer of the TCP/IP model The functions of the kernel, service, and command layers of an operating system are as follows: Function of the command layer: The command layer of an operating system is the interface of the user toward operating system either in textual or graphical form. Thus, the command layer accepts the keyboard or the mouse clicks from users which are then translated into the commands of the operating system. Function of the service layer: The service layer of the operating system thus contains the set of the various functions that can be easily executed by the application programs and also with the command layer. Function of the kernel: The kernel main function is to manage the resources and thus helps in interacting directly with the hardware of the computer using the device drivers, while allocates and interacts with these types of the resources for the functions of the service layers.
Processors A multitasking OS supports multiple active processes or users. A multitasking or a multi-user operating system allows the multiple users on various terminals or computers to access one system concerned with one operating system.