the creation of computer viruses

... bytes of data in the Disk Transfer Area, or DTA This data provides the program doing the search with the name of the file which DOS just found, its attribute, its size and its date of creation ... the data in the DTA is not altered between the call to Search First and later calls to Search Next, because the Search Next expects the data from the last search call to be there Of course, the ... allocate room for the PSP, and load the program file at offset 100H To determine the number of bytes the virus will need automatically, we simply put a label VIRUS at the start of the virus code

Ngày tải lên: 14/08/2014, 18:22

... Initial value of the code ment relative to the start of the code in the EXE file This is modified by DOS at load time. 18H 2 Relocation Tbl Offset Offset of the start of the relocation ... move the first five bytes of the original host program from the data area START_CODE where they are stored to the start of the host program at 100H, Finally, the virus must transfer control to the ... priori assumptions about the size of the file, or what is code or data All of this information is stored in the EXE file itself, in the EXE Header at the beginning of the file This Trang 7header

Ngày tải lên: 14/08/2014, 18:22

... copy of the virus If there is a problem at any stage of the infection process, the virus will simply abort, and no permanent damage will be done to the disk On the other hand, we could design the ... called The two responsibilities of the viral boot sector are to load the main body of the virus into memory, and then to load and execute the original boot sector When the BIOS loads the viral ... cluster is empty, the corresponding FAT entry is 0 If it is in the middle of a file, the FAT entry is a pointer to the next cluster in the file; if it is at the end of a file, the FAT entry is

Ngày tải lên: 14/08/2014, 18:22

... NUMRELS 109 The Little Black Book of Computer Viruses Trang 9; d) The word VIRUSID must not appear in the 2 bytes just before; the initial CS:0000 of the test file If it does, the virus ; ... a) The signature field in the EXE header must be ’MZ’ (These ; are the first two bytes in the file.) ; b) The Overlay Number field in the EXE header must be zero ; c) There must be room in the ... ES:DI pointing to the end of the first string in the ;destination (or the first character of the second string, after moved) ; CONCAT: mov al,byte ptr es:[di] ;find the end of string 1 inc

Ngày tải lên: 14/08/2014, 18:22

... ;the data area at the beginning of the boot sector. MOVE_DATA: MOV SI,OFFSET DSKBASETBL ;Move the boot sector code MOV DI,OFFSET DISK_BUF + (OFFSET DSKBASETBL - OFFSET BOOT- SEC) MOV CX,OFFSET ... and ;the data area at the beginning of the boot sector. MOVE_DATA: MOV SI,OFFSET DSKBASETBL ;Move boot sec code after data MOV DI,OFFSET DISK_BUF+(OFFSET DSKBASETBL-OFFSET BOOTSEC) MOV CX,OFFSET ... DW ? ;Location of AA55H in boot sector loaded at DISK_BUF ;Here is the start of the boot sector code. This is the chunk we will take out ;of the compiled COM file and put it in the first sector

Ngày tải lên: 14/08/2014, 18:22

... > 1 If the disk is infected, ;then instead of reading the true data there, return a block of 0’s, since ;0 is the data stored in a freshly formatted but unused sector This will ;fake the caller ... putting the present boot sector in Sector 6 with the virus ;code in sectors 1 through 5, and then replacing the boot sector on the disk ;with the viral boot sector INFECT_360K: mov dl,al ;read the ... INF360_EXIT push ax mov di,OFFSET BOOT_DATA ; mov si,OFFSET SCRATCHBUF + (OFFSET BOOT_DATA - OFFSET BOOT_START) mov si,OFFSET SB_BOOT_DATA ;required instead of ^ for A86 mov cx,32H /

Ngày tải lên: 14/08/2014, 18:22

... moves the pointer relative to the beginning of the file, al=1 moves the pointer relative to the current location, al=2 moves the pointer relative to the end of the file. Function 43H: Get and ... Written by the creators of the Phoenix BIOS, this book details all of the various BIOS functions and how to use them It is a useful complement to the AT Technical Reference, as it discusses how the ... bytes from the file referenced by handle bx into the buffer ds:dx The data is read from the file starting at the current file pointer The file pointer is initialized to zero when the file is

Ngày tải lên: 14/08/2014, 18:22

... File size The in-core copy of the inode contains the following fields in addition to the fields of the disk inode: 9 The status of the in-core inode 9 The logical device number of the file system ... number of free blocks in the file system 9 A list of free blocks available on the file system 9 The index of the next free block in the free block disk 9 The size of the inode list 9 The number of ... (University of Southern California) is the first formal work in the field of computer viruses He also wrote "Computer Viruses-Theory and Experiments" in 1987, this paper brought the term "computer

Ngày tải lên: 18/02/2021, 08:01

... furthering the interests of another country at the expense of Australia’s interests.9 atten-The end of the Cold War, the rise of al Qaeda, preparations for the 2000 Olympic Games in Sydney, the ... Office of the Secretary of Defense, the Joint Staff, the Unified Combatant Commands, the defense agencies, the Department of the Navy, the Marine Corps, the U.S Coast Guard, the U.S Intelligence Community, ... challenges in doing 7 Of these issues, the first two—the difficulty of identifying a small number of threatening individuals against a large background of other people and the need for adaptability—are

Ngày tải lên: 15/03/2014, 21:20

... appropriate of the educational theories upon which to base the interactive computer programme They revolve around the idea of a zone of proximal development This represents the difference between what the ... countries on the role of diet in caries prevention All fifty four of the experts and all of the national guidelines mentioned “reduction of the frequency of cariogenic intakes” as the principle ... [1.5.2] Computers in the classroom The numbers of computers in preschools and primary one classroom‟s has risen dramatically over the last ten years to almost the point of saturation The presence of

Ngày tải lên: 28/03/2014, 20:20

... at the Oxford Centre for Industrial and Applied Mathematics. Professor of Computer Science at the University of Bristol. Professor (Emeritus) of Banking and Finance at the London School of ... full the objectives they are directed at A joint initiative from a European Office of Financial Research and the US Office of Financial Research (OFR), with the involvement of other ... impact of. .. its findings are entirely independent of the UK Government As such, the findings do not represent the views of the UK or any other government, or the views of any of

Ngày tải lên: 29/03/2014, 18:20

... emergence of world class corporate hospitals, large pool of medical manpower, and young population across a variety of seg-ments The second conclusion is that given the nature of many of the constraints ... Health professionals are regulated at the level of Mem-ber States and, to some extent, at the EU level [8] There are two broad regimes for recognition of qualifi-cations in the EU: (a) the sectoral ... specificacertifica-tion of minimum training, and other conditions for the medical profession Such regulations are likely to influence the ability of profes-sionals and establishments to supply health services to the

Ngày tải lên: 11/08/2014, 14:21

... contributions from the social sciences that allow a better comprehension of the phenomenon of the creation of Trang 3the health consumer as part of the biomedicalization ledby the medical industrial ... increased the amount of pharmaceutical products in the market, but additional strategies were required to increase the demand of the products The capture of the supply side (providers) of the health ... while the corporate groups managing financial capital were increasing their shares of the health market We observed that as a consequence of the mas-sive adoption of managed care in the U.S and other

Ngày tải lên: 11/08/2014, 14:21

... Huu Tong… There is one common thing in the above mentioned studies which is the importance of establishing the issue to be the centre of the method, and students are encouraged to find the solutions ... particular and activation method for CA of student - Investigate current status of experimenting with the aid of Com in HS - Study the usage of experimenting with the aid of Com in 11th grade “Electrics” ... teaching test to evaluate performance of the new method 7 Contribution of the thesis - Study, use experimenting with the aid of Com to teach PS some lessons of chapter “Currents in different environment

Ngày tải lên: 24/08/2014, 14:01

... Sequence ID ID’s where the information belongs in relation to the rest of the information End of Message ID’s the end of the packet Fiber Optic Cable Switches and Hubs Trang 23The InternetHow Information ... radio signal (series of beeps). Trang 21The InternetThe simplest definition of the Internet is that it's a network of computer Fiber Optic Cable Switches and Hubs Trang 22The InternetHow Information ... reassembled Each part of the packet has a specific function: Header Provides the complete destination address for the packet Data Block The portion of the overall information carried by the packet Sequence

Ngày tải lên: 24/10/2014, 13:22

... the search with the name of the file which DOS just found, its attribute, its size and its date of creation. Some of the data reported in the DTA is also used by DOS for performing the Search Next ... of memory, and the offset register tells how many bytes to add to the start of the 16 byte block to locate the desired byte in memory. For example, if the ds register is set to 1275 Hex and the ... 00 At 80H we find the value 0EH, which is the length of “Hello there!”, followed by the string itself, terminated by <CR>=0DH. Likewise, the PSP contains the address of the system environment,...

Ngày tải lên: 19/03/2014, 13:43

... far. Not so, the computer virus, because it attaches itself to otherwise useful programs. The computer user will execute these programs in the normal course of using the computer, and the virus ... up with plenty of good reasons why fiat creation can’t occur. In the world of bits and bytes, many of these philosophical conundrums just disappear. (The fiat creation of computer viruses 6 Please ... viruses 2. Companion viruses 3. Parasitic viruses If you can understand these three simple types of viruses, you will already understand the majority of viruses being written today. Most of them...

Ngày tải lên: 14/08/2014, 18:22

... relative to the start of the code in the EXE file. This is relocated by DOS at load time. 18H 2 Reloc Tbl Offset Offset of the start of the relocation table from the start of the file, in ... be the first byte of the virus. 3. Write the virus code currently executing to the end of the EXE file being attacked. 4. Write the initial value of ss:sp, as stored in the EXE Header, to the location ... [FFF8H] The first is the address 100H, used to return from the subroutine just placed on the stack to offset 100H, where the host will be. The next is the address of the routine hiding just under the...

Ngày tải lên: 14/08/2014, 18:22

... free at the time of the ;execution of the boot sector. ORG 0500H DISK_BUF: DB ? ;Start of the buffer ;Here is the start of the boot sector code. This is the chunk we will take out ;of the compiled ... SEC_SIZE - 1]/SEC_SIZE and the size of the file in sectors. The file size in bytes is stored at offset 1CH from the start of the directory entry at 0000:0500H. The number of sectors to load is SIZE ... loading, the virus would have crashed the system. (And that, incidently, is why the virus we’re discussing is the Kilroy-B. The Kilroy virus dis- cussed in The Little Black Book of Computer Viruses...

Ngày tải lên: 14/08/2014, 18:22

... writes. First, DEVIRUS finds the end of the host file and uses that as the offset for the new STRAT routine, writing this value into the header. Next it hides the address of the old STRAT routine internally ... STRAT routine internally in itself at STRJMP, and then writes the body of its code to the end of the SYS file. That’s all there is to it. The logic of DEVIRUS is depicted in Figure 14.3, and its ... as the data segment selector, once we have finished defining it. 3. Define the base of the segment associated to the new descriptor. This is the linear address of where that segment starts. The...

Ngày tải lên: 14/08/2014, 18:22