Question

DHULI 3.1 Explain what a buffer overflow is (3 marks) and give three implications of a buffer overflow (3 marks). 3.2 Explain the following programming errors: (6) Incomplete mediation • TOCTTOU Undocumented access point Off-by-one error 3E 3.3 Discuss seven ways in which a virus can be executed.

Answer 1

3.1 What is Buffer Overflow Buffers are memory Storage regions that temporarily hold data while it is being transferred from one location to another A Buffer overflow is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory locations. Implications of a Buffer overflow two types of implications There are mainly 1) Stack Overflow î) Heap Overflow Stack Overflows are more common and leverage stack memory that only exists during the existing time of function Heap Overflows are harder to carry out and involve flooding the memory space allocated for a program beyond memory used for Current runtime operations. Scanned with CamScanner

Program Errors * Incomplete Mediation To prevent a buffer overflow, the program validates the input by checking the length of input before attempting to write it to hufter failure to do so is an Example of Incomplete mediation Тос TTou It means Time of Check To Time of Use. It is a class of bugo caused bey changes in a system between the Checking of a condition and the use of the results of that check. It is a Race condition. * Undocumented Access Point It is also known as "Back door or "Trap door". Trapdoor is a secret undocumented entry point into a program used to grant aress withour usual methods of access authentication. A traf is a software interrupte

* Off-by - One - Error It is a Logical error, when we have <= " instead of "c" when we are checking the expression in the loop. The example below to understand more int array [ = new int [5]; for (int ico. i<= 5 ; it to System, out.printin (array cin); The program will result in array out of Bounds exception. Scanned with CamScanner

3.3 Ways in which a virus can be executed ypes of Different computer Viruses 1. Boot Sector wirus This type of virus can take control when you start or boot your computer, It can be spread by inserting an infected USB drive into your computer 2. Web Scripting Virus This type of virus exploits the code of web browsers and web pages. If you access such a website, the virus can infect your computer 3. Browser Hijacker This type of virus bijacks certain web browser functions and you may be directed to an un inteded website automatically Resident Virus This type of virus inserts itself 6 in a computer Systems memory. It can recute anytime when os loads.

5. Direct Action virus This type of virus attacks when you execute a file containing virus Otherwise it will do nothing 6. Polymorphic virus This type of virus changes its code each time an infected file executed. It does this To avoid antivirus programs 7. File infector virus this common virus inserts malicious Code into executable files files used to perform certain functions or operations on a system. 8. Mutripartite virus This types of virus infects and spreads in multiple ways. It can infect both program files and system sectors. 9. Macro Virus This type of virus infect when you open an infected document through email attachments.. \CS