diff --git a/cmake/externals/glm/CMakeLists.txt b/cmake/externals/glm/CMakeLists.txt
index 1fa393e69e..1afa9a89e8 100644
--- a/cmake/externals/glm/CMakeLists.txt
+++ b/cmake/externals/glm/CMakeLists.txt
@@ -4,6 +4,7 @@ include(ExternalProject)
 ExternalProject_Add(
   ${EXTERNAL_NAME}
   URL http://pkgs.fedoraproject.org/repo/pkgs/glm/glm-0.9.5.4.zip/fab76fc982b256b46208e5c750ed456a/glm-0.9.5.4.zip
+  URL_MD5 fab76fc982b256b46208e5c750ed456a
   CMAKE_ARGS -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   LOG_DOWNLOAD ON
 )
diff --git a/cmake/externals/gverb/CMakeLists.txt b/cmake/externals/gverb/CMakeLists.txt
index c62284a133..4173efa073 100644
--- a/cmake/externals/gverb/CMakeLists.txt
+++ b/cmake/externals/gverb/CMakeLists.txt
@@ -8,6 +8,7 @@ include(ExternalProject)
 ExternalProject_Add(
   ${EXTERNAL_NAME}
   URL http://hifi-public.s3.amazonaws.com/dependencies/gverb-master.zip
+  URL_MD5 8b16d586390a2102804e46b87820dfc6
   CMAKE_ARGS ${ANDROID_CMAKE_ARGS} -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   LOG_DOWNLOAD ON
 )
diff --git a/cmake/externals/soxr/CMakeLists.txt b/cmake/externals/soxr/CMakeLists.txt
index 49d7c7598a..2b00db883a 100644
--- a/cmake/externals/soxr/CMakeLists.txt
+++ b/cmake/externals/soxr/CMakeLists.txt
@@ -8,6 +8,7 @@ include(ExternalProject)
 ExternalProject_Add(
   ${EXTERNAL_NAME}
   URL http://hifi-public.s3.amazonaws.com/dependencies/soxr-0.1.1.zip
+  URL_MD5 349b5b2f323a7380bc12186d98c77d1d
   CMAKE_ARGS ${PLATFORM_CMAKE_ARGS} -DBUILD_SHARED_LIBS=1 -DBUILD_TESTS=0 -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
   LOG_DOWNLOAD ON
 )
diff --git a/cmake/externals/tbb/CMakeLists.txt b/cmake/externals/tbb/CMakeLists.txt
index cbf7d80c68..e5243edf8c 100644
--- a/cmake/externals/tbb/CMakeLists.txt
+++ b/cmake/externals/tbb/CMakeLists.txt
@@ -9,6 +9,7 @@ if (ANDROID)
   ExternalProject_Add(
     ${EXTERNAL_NAME}
     URL http://hifi-public.s3.amazonaws.com/dependencies/tbb43_20150209oss_src.tgz
+    URL_MD5 f09c9abe8ec74e6558c1f89cebbe2893
     BUILD_COMMAND ${NDK_BUILD_COMMAND} --directory=jni target=android tbb tbbmalloc arch=arm
     BUILD_IN_SOURCE 1
     CONFIGURE_COMMAND ""
@@ -18,10 +19,13 @@ if (ANDROID)
 else ()
   if (APPLE)
     set(DOWNLOAD_URL http://s3.amazonaws.com/hifi-public/dependencies/tbb43_20150209oss_osx.tgz)
+    set(DOWNLOAD_MD5 3e683c19792582b61382e0d760ea5db2)
   elseif (WIN32)
     set(DOWNLOAD_URL http://s3.amazonaws.com/hifi-public/dependencies/tbb43_20150209oss_win.zip)
+    set(DOWNLOAD_MD5 e19c184f2bb0e944fc5f397f1e34ca84)
   else () 
     set(DOWNLOAD_URL http://s3.amazonaws.com/hifi-public/dependencies/tbb43_20150209oss_lin.tgz)
+    set(DOWNLOAD_MD5 d9c2a6f7807df364be44a8c3c05e8457)
   endif ()
   
   ExternalProject_Add(