Your arduino board is receiveing somthing like:
"is message was sent to you by 10-Strike Network Monitor for the "
probably encode as UTF-16. Since it is just a piece of the message it is difficult to understand the byte order (big or little endian).
Empirically, you may build your string using just the 2
nd,4
th,6
th.. characters, i.e.
loop(){
String message;
char c ;
int count = 0;
while ( Serial1.available() ) {
c = Serial1.read();
if (count % 2) message += c;
count++;
}
}