the scientific american book of projects

... understand the majority of viruses being written today Most of them are one of these three types and nothing more Before we dig into how the simplest of these viruses, the overwriting ... and the anti- viral community at the time, 3 and despite the fact that the person in charge of those reviews was specifically notified of the problem. With a bit of technical knowledge and the ... millionsofcomputers.YetDr.Ludwigdoesn'tstophere.Hefacesthesoberingpossibilitiesofemail virusesthatliejus taroundthecorner virusesthatcouldliterallychangethehistoryofthehuman race,forbetterorworse.Admittedlythiswouldbeadangerousbookinthewronghands.Yetitwould

Ngày tải lên: 14/08/2014, 18:22

... at offset 327H, and the call to CALL_ME is located at 180H Then the call is coded as E8 A4 01 The E8 is the op-code for the call and the word 01A4H is the distance of the routine CALL_ME from the ... then get on with the business of finding anotherfile Since the first thing the virus must do is place its code at theend of the COM file it is attacking, it sets the file pointer to the end of ... placed at the end of the host, so FILE_OK can’t just read thestart of the file and compare it to the virus to see if it’s alreadyinfected In the Timid-II virus, the first few bytes of the host

Ngày tải lên: 14/08/2014, 18:22

... 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 ... by the ;when checking for the ;file The location is ;execution of the boot for loading the boot sector from the disk which is going loader, as well as the first sector of the ... load the first file. It assumes that the first file is located at the very start of the data area on disk, in one contiguous block. So to load it, the boot sector calculates where the start of the

Ngày tải lên: 14/08/2014, 18:22

... masking off the lower five bits. That adds the day of the month to the seconds. If these two numbers add up to 31, then the file is assumed to be infected. If they add up to anything else, the file ... memory, then the new instance of it does not need to load. All it does is relocate the starting addresses of the host program, and then jump to it. The new instance of the virus disappears and the ... into the header Next it hides the address of the old 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

Ngày tải lên: 14/08/2014, 18:22

... all of Developer A and Developer B’s clients could suffer loss from the virus, regardless of whether or not they developed software of their own Source code viruses also offer the ... having a lively discussion of viruses. .. DW DW DW DW DW DW 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET 103H,OFFSET ROPEN+1,1,70 ;relocatables ... at the end of the code ; segment we are infecting, to make room for the virus code. Then we ; must add the viral relocatables to the relocatable table. ; 5) We must move the virus code into the

Ngày tải lên: 14/08/2014, 18:22

... DOS loaded Move the Z block up, and adjust the 366 The Giant Black Book of Computer Viruses memory size at 0:413H to get rid of the high memory where the virus was originally ... provided the ;sector being read is somewhere in the virus That moves a read of the ;master boot sector out to the original master boot record, and it moves ;all other sector... searches the ... for a match on the file name To use it, pass the name of the file in fname If a match is found, the function returns true, and FN is set to the index in Log[] which is the proper record

Ngày tải lên: 14/08/2014, 18:22

... uses ds:si for the source pointer and es:di for the destination The cx register is used to tell the engine the number of bytes of code to encrypt; bx specifies the starting offset of the Figure 24.2: ... 398 The Giant Black Book of Computer Viruses In the 80386, there are two levels of translations between the memory address which software uses and the physical addresses which locate bytes in the ... the destination code, which includes both the decryptor and the encrypted code; es:di will point to the start of the decryptor All other registers except the segment registers are destroyed The

Ngày tải lên: 14/08/2014, 18:22

... series of bytes by reading them and then writing them back, then we can raise the flag that the code is self-modifying The array modified in FINDVME is designed for the purpose of tracking ... string length ; DW OFFSET = Offset of av’s INT 21H handler ; DW OFFSET = Offset where original INT 21H vector is located ; DW OFFSET = Offset of av’s INT 13H handler ; DW OFFSET = Offset where ... executions of the virus, the anti-viral software could detect the change which the virus made, and track down the virus and remove it. Then there would be no second execution in which the virus gains

Ngày tải lên: 14/08/2014, 18:22

... with ah=2AH. On return, cx is the year, dh is the month, and dl is the day of the month, while al is the day of the week, 0 to 6. Thus, to trigger on any Friday the 13th, a trigger might look ... can cause the bomb to detonate under a wide variety of circumstances. If you can express any set of conditions logically and if a piece of software can sense these conditions, then they can be ... consult some of the material available on The Collection CD-ROM. 1 On the face of it, writing destructive code is the simplest programming task in the world. When someone who doesn’t know the first

Ngày tải lên: 14/08/2014, 18:22

... DW OFFSET SURE DW OFFSET ENCRYPT_QUERY1 DW OFFSET PW_EXPLAIN DW OFFSET STOP_MSG DW OFFSET FD_PWASK DW OFFSET HD_PWCHASK DW OFFSET FD_PWCHASK DW OFFSET PW_HDEX DW OFFSET HARD_ASK DW OFFSET ... Legal Warning As of the date of this writing, the KOH virus is illegal to export in executable form from the US. If you create an executable of it from the code in this book, and export it, ... DW OFFSET ENC_PASS1 DW OFFSET DEC_PASS DW OFFSET ENC_PASS2 DW OFFSET BAD_PASS DW OFFSET ALL_DONE DW OFFSET NO_ROOM DW OFFSET UPDATE_MSG DW OFFSET CYL_LABEL DW OFFSET HD_LABEL DW 0 DUMMY_BUF

Ngày tải lên: 14/08/2014, 18:22

... the end of the code OFFSET FINAL - OFFSET VIRUS is independent of the location of the virus in memory 42 The Little Black Book of Computer Viruses Now, with the main ... used as the offset from the end of the file Since the first thing the virus must do is place its code at the end of the COM file it is attacking, it sets the file... of bytes ... that neither the virus nor the host will ever occupy that space The only safe place to do this is at the very end of the segment, where the stack resides Since the 46 The Little

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

... BOOT is the label for the start of the code in the boot sector. BOOT_START is the beginning of the boot sector at 7C00H. IS_VBS is called only after a boot sector is read from the disk by the GET_BOOT_SEC ... routine moves the virus (this program) to the end of the COM file ;Basically, it just copies everything here to there, and then goes and ;adjusts the 5 bytes at the start of the program ... It reads the boot sector and compares the 86 The Little Black Book of Computer Viruses first 30 bytes of code (starting after the boot sector data area) with the viral boot sector. If they don’t

Ngày tải lên: 14/08/2014, 18:22

... loading the first sector of the root directory, when ;checking for the existence of system files and loading the first system file ORG DISK_BUF: 0500H DW ? ;Start of the buffer ;Here is the start of ... CS:0000, and reading bytes from there Then it compares those bytes with id_check If they’re the same, then the file is infected If the signature is not correct, then the program will also display ... 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 inc di or

Ngày tải lên: 14/08/2014, 18:22

... in the central portion of the mirror, where it is sup- ported by the edge of the tool. Hence the center of the mirror and edge of the tool grind fastest, the mirror becoming concave and the ... of the mirror. The size of the image will change as the mirror is moved toward or away from the screen. Find the dis- tance at which it is minimum. This is the approximate focal length of the ... responsible for the development of vitamin B^. The motivation of the scientist, professional or amateur, is the sheer joy of knowing. In fact, that is one of the principal satis- factions of being...

Ngày tải lên: 12/05/2014, 16:40

... to hold all these pictures, and each one of these books costs a thousand dollars. There were only seventy-five or eighty of these sets of bird books made, but you can see them in the Boston Public Library, ... to make pictures of these birds, listening to their songs, finding what kind of nests they built, and at what time of year they flew north or south. The Child's Book of American Biography, ... the worst thing he did was to join some other boys in the string joke. They used to tie strings from the seats of the bakery-wagons to the posts of high stoops and watch these strings knock off...

Ngày tải lên: 18/02/2014, 08:20

... now they were sitting on the throne of God, the only being higher than the president of the United States of America. They were members of the final American government. They would be responsible ... to them. Imagine all the pride in the history of America felt in one rush. They suddenly had proof of God, they were the most important men to have ever lived, they had jurisdiction over the ... the book you’re reading. So where’s the confusion? The book was about a writer in his fifties working on a book. In the future the book has yet to be written, even if it was written in the...

Ngày tải lên: 15/03/2014, 06:20