Added README text

README

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+icmpsh - simple reverse ICMP shell
+
+icmpsh is a simple reverse ICMP shell with a win32 slave and a POSIX compatible master in C, Perl or Python.
+
+
+--- Running the Master ---
+
+The master is straight forward to use. There are no extra libraries required for the C version. 
+The Perl master however has the following dependencies:
+
+	* IO::Socket
+	* NetPacket::IP
+	* NetPacket::ICMP
+
+
+When running the master, don't forget to disable ICMP replies by the OS. For example:
+
+	sysctl -w net.ipv4.icmp_echo_ignore_all=1
+
+If you miss doing that, you will receive information from the slave, but the slave is unlikely to receive
+commands send from the master.
+
+
+--- Running the Slave ---
+
+The slave comes with a few command line options as outlined below:
+
+
+-t host            host ip address to send ping requests to. This option is mandatory!
+
+-r                 send a single test icmp request containing the string "Test1234" and then quit. 
+		   This is for testing the connection.
+
+-d milliseconds    delay between requests in milliseconds 
+
+-o milliseconds    timeout of responses in milliseconds. If a response has not received in time, 
+		   the slave will increase a counter of blanks. If that counter reaches a limit, the slave will quit.
+                   The counter is set back to 0 if a response was received.
+
+-b num             limit of blanks (unanswered icmp requests before quitting
+
+-s bytes           maximal data buffer size in bytes
+
+
+In order to improve the speed, lower the delay (-d) between requests or increase the size (-s) of the data buffer.