mirror of
https://github.com/vxunderground/MalwareSourceCode
synced 2024-06-30 19:02:32 +00:00
203 lines
4.2 KiB
NASM
203 lines
4.2 KiB
NASM
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TITLE DRIP 5-26-87 [4-21-88]
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;Goes TSR, activate/toggle with Scroll Lock key.
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;Characters randomly drip down/off the screen
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LF EQU 0AH
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CR EQU 0DH
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;
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Cseg SEGMENT
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ASSUME DS:Cseg, SS:Cseg ,CS:Cseg ,ES:Cseg
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ORG 100H
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Drip proc near
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JMP Start
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int8Vec dd 0 ;save old Int 8 vector
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saveDI dw 0
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saveSI dw 0
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video dw 0B000H ;default mono screen memory
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wcntr_13A dw 40H ;counter
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byte_13C DB 0FFH
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bflag_13D DB 0
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bcntr_13E DB 0
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bflag_13F DB 0
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bcntr_140 DB 0
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word_2BE dw 0
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Drip endp
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NewInt8 proc far
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ASSUME DS:Nothing
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PUSHF ;save user's flags
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PUSH AX ;and his Int 8 request
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MOV AH,2 ;get shift status
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INT 16H
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AND AL,10H ;mask for Scroll Lock key
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JZ Continue_Int8 ; continue to Int 8
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CMP CS:bcntr_13E,0 ;counter zeroed?
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JZ L01A0 ; yep, time to act
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DEC CS:bcntr_13E ;decr counter
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JMP SHORT Continue_Int8
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L01A0: CMP CS:bflag_13D,0 ;flag set?
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JNZ Continue_Int8 ; yep, just continue to Int 8
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JMP SHORT L01B2 ;time to act
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Continue_Int8:
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POP AX ;restore user's Int 8 svc
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POPF ;restore user's flags
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JMP CS:int8Vec ;jump to old Int 8
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L01B2: PUSHF ;save flags
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CALL CS:int8Vec ;call old Int 8
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PUSH ES ;save all his regs
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PUSH DS
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PUSH DX
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PUSH CX
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PUSH DI
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PUSH SI
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mov ax,CS
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mov DS,ax
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ASSUME DS:Cseg
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MOV AX,video
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MOV ES,AX
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ASSUME ES:Nothing
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cmp bflag_13F,0 ;flag clear?
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JZ L01D9 ; yep
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MOV DI,saveDI ;get our screen pointers
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MOV SI,saveSI
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STI ;enable ints
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JMP SHORT MoveChar ;go to work
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L01D9: MOV bflag_13D,0FFH ;set flag
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STI ;enable interrupts
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MOV bcntr_140,64H ;refresh counter
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Lup1E4: CMP bcntr_140,0 ;zeroed out?
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JNZ L01EE ; nope
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JMP Pop_Iret ; return
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L01EE: DEC bcntr_140 ;count down
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CALL L02AC
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AND AX,0FFEH
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MOV SI,AX
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MOV AL,ES:[SI]
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CMP AL,20H ;just a space?
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JZ Lup1E4 ; yep, try again
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or al,al ;just a zero?
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JZ Lup1E4 ; yep, try again
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CMP SI,0FA0H ;screen bottom?
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JNB Lup1E4 ; not yet, try again
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MOV DI,SI ;point to new char location
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ADD DI,0A0H ;move this far each time (1 line)
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CMP DI,0FA0H ;screen bottom?
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JNB L025B ;not yet, continue
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MOV AL,ES:[DI] ;get char at new location
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CMP AL,20H ;just a space?
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JZ Save_Iret ;yep, save screen ptrs, Iret
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or al,al ;just a zero?
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JNZ Lup1E4 ; yep, continue
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Save_Iret:
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MOV saveDI,DI ;save screen pointers
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MOV saveSI,SI
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MOV bflag_13F,0FFH ;reset flag
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JMP SHORT Pop_Iret ;return
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MoveChar:
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MOV bflag_13F,0 ;turn flag off
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MOV AL,ES:[SI] ;snarf screen char
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MOV ES:[DI],AL ;move it here
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MOV BYTE PTR ES:[SI],20H ;blank out old char
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MOV SI,DI
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ADD DI,0A0H
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CMP DI,0FA0H ;screen bottom?
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JNB L025B ; not yet
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MOV AL,ES:[DI] ;get char
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CMP AL,20H ;just a space?
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JZ Save_Iret ; yep, save ptrs, Iret
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or al,al ; a 0?
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JZ Save_Iret ; yep, save ptrs, Iret
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JMP SHORT L025F
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L025B: MOV BYTE PTR ES:[SI],20H ;stuff space on screen
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L025F: DEC wcntr_13A ;decrement counter
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JNZ L026F
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SHR byte_13C,1
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MOV wcntr_13A,40H ;refresh counter
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L026F: CALL L02AC
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AND AL,byte_13C
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MOV bcntr_13E,AL
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Pop_Iret:
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POP SI
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POP DI
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POP CX
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POP DX
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POP DS
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POP ES
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POP AX
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POPF
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MOV CS:bflag_13D,0 ;clear flag
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IRET
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NewInt8 endp
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L02AC proc near
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MOV AX,word_2BE
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PUSH AX
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AND AH,0B4H
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POP AX
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JPE L02B7
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STC
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L02B7: RCL AX,1
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MOV word_2BE,AX
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RET
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L02AC endp
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Start proc near
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MOV ax,3508H ;get Int8 vector
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INT 21H
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mov word ptr int8Vec,bx ;save ofs
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mov word ptr int8Vec+2,ES ;save seg
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MOV AH,2CH ;get DOS system time
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INT 21H
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MOV word_2BE,DX ;save seconds, deciseconds
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MOV bcntr_13E,0FFH ;refresh counter
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MOV AH,0FH ;get current video mode
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INT 10H
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CMP AL,6 ;?
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JZ Use_Mono ; yep
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CMP AL,7 ;mono?
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JZ Use_Mono ;yep
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MOV video,0B800H ;use color screen
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Use_Mono:
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MOV DX,OFFSET NewInt8 ;DS:dx = our service
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mov ax,2508H ;set new Int 8 vector
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INT 21H
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MOV DX,offset Start ;program end
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MOV CL,4
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SHR DX,CL ;compute size in paras
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INC DX ;safeside
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MOV AH,31H ;advanced TSR
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INT 21H
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DB 'DRIP Version 2.01',0 ;,CR,LF
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DB 'G. Masters 5/25/87',0 ;,CR,LF
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db 'Toad Hall 880421',0
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; DB 1AH
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; DB 90H
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Start endp
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Cseg ENDS
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END Drip
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