diff --git a/README.md b/README.md
index 6a291d8..0cac152 100644
--- a/README.md
+++ b/README.md
@@ -245,6 +245,8 @@ the [browser malware](#browser-malware) section.*
 
 * [NoMoreXOR](https://github.com/hiddenillusion/NoMoreXOR) - Guess a 256 byte
   XOR key using frequency analysis.
+* [xortool](https://github.com/hellman/xortool) - Guess XOR key length, as
+  well as the key itself.
 
 ## Debugging and Reverse Engineering