Index: clang-tidy/cert/CERTTidyModule.cpp
===================================================================
--- clang-tidy/cert/CERTTidyModule.cpp
+++ clang-tidy/cert/CERTTidyModule.cpp
@@ -17,6 +17,7 @@
 #include "../misc/StaticAssertCheck.h"
 #include "../misc/ThrowByValueCatchByReferenceCheck.h"
 #include "CommandProcessorCheck.h"
+#include "DontModifyStdNamespaceCheck.h"
 #include "FloatLoopCounter.h"
 #include "SetLongJmpCheck.h"
 #include "StaticObjectExceptionCheck.h"
@@ -33,6 +34,8 @@
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     // C++ checkers
     // DCL
+    CheckFactories.registerCheck<DontModifyStdNamespaceCheck>(
+        "cert-msc53-cpp");
     CheckFactories.registerCheck<VariadicFunctionDefCheck>(
         "cert-dcl50-cpp");
     CheckFactories.registerCheck<misc::NewDeleteOverloadsCheck>(
Index: clang-tidy/cert/CMakeLists.txt
===================================================================
--- clang-tidy/cert/CMakeLists.txt
+++ clang-tidy/cert/CMakeLists.txt
@@ -3,6 +3,7 @@
 add_clang_library(clangTidyCERTModule
   CERTTidyModule.cpp
   CommandProcessorCheck.cpp
+  DontModifyStdNamespaceCheck.cpp
   FloatLoopCounter.cpp
   SetLongJmpCheck.cpp
   StaticObjectExceptionCheck.cpp
Index: clang-tidy/cert/DontModifyStdNamespaceCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/cert/DontModifyStdNamespaceCheck.h
@@ -0,0 +1,36 @@
+//===--- DontModifyStdNamespaceCheck.h - clang-tidy--------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DONT_MODIFY_STD_NAMESPACE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DONT_MODIFY_STD_NAMESPACE_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace cert {
+
+/// Modification of the std or posix namespace can result to undefined behavior.
+/// This checker warns for such modifications.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/cert-msc53-cpp.html
+class DontModifyStdNamespaceCheck : public ClangTidyCheck {
+public:
+  DontModifyStdNamespaceCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace cert
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_CERT_DONT_MODIFY_STD_NAMESPACE_H
Index: clang-tidy/cert/DontModifyStdNamespaceCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/cert/DontModifyStdNamespaceCheck.cpp
@@ -0,0 +1,40 @@
+//===--- DontModifyStdNamespaceCheck.cpp - clang-tidy----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DontModifyStdNamespaceCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace cert {
+
+void DontModifyStdNamespaceCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(namespaceDecl(unless(isExpansionInSystemHeader()),
+                                   anyOf(hasName("std"), hasName("posix")))
+                         .bind("nmspc"),
+                     this);
+}
+
+void DontModifyStdNamespaceCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *Nmspc = Result.Nodes.getNodeAs<NamespaceDecl>("nmspc");
+
+  std::string namespaceName = Nmspc->getName();
+
+  diag(Nmspc->getLocation(), "Modification of " + namespaceName +
+                                 " namespace can result to undefined behavior");
+}
+
+} // namespace cert
+} // namespace tidy
+} // namespace clang
+
Index: docs/clang-tidy/checks/cert-msc53-cpp.rst
===================================================================
--- /dev/null
+++ docs/clang-tidy/checks/cert-msc53-cpp.rst
@@ -0,0 +1,6 @@
+.. title:: clang-tidy - cert-msc53-cpp
+
+cert-msc53-cpp
+==============================
+
+Modification of the std or posix namespace can result to undefined behavior. This checker warns for such modifications.
Index: docs/clang-tidy/checks/list.rst
===================================================================
--- docs/clang-tidy/checks/list.rst
+++ docs/clang-tidy/checks/list.rst
@@ -9,6 +9,7 @@
    cert-dcl50-cpp
    cert-dcl54-cpp (redirects to misc-new-delete-overloads) <cert-dcl54-cpp>
    cert-dcl59-cpp (redirects to google-build-namespaces) <cert-dcl59-cpp>
+   cert-msc53-cpp
    cert-env33-c
    cert-err34-c
    cert-err52-cpp
Index: test/clang-tidy/cert-dont-modify-std-namespace.cpp
===================================================================
--- /dev/null
+++ test/clang-tidy/cert-dont-modify-std-namespace.cpp
@@ -0,0 +1,44 @@
+// RUN: %check_clang_tidy %s cert-msc53-cpp %t -- -- -std=c++1z
+
+namespace A {
+  namespace B {
+    int b;
+  }
+}
+
+namespace A {
+  namespace B {
+    int c;
+  }
+}
+
+namespace posix {
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: Modification of posix namespace can result to undefined behavior [cert-msc53-cpp]
+  namespace vmi {
+  }
+}
+
+namespace std {
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: Modification of std namespace can result to undefined behavior [cert-msc53-cpp]  
+  int stdInt;
+}
+
+namespace foobar {
+  namespace std {
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: Modification of std namespace can result to undefined behavior [cert-msc53-cpp]  
+  }
+}
+
+namespace posix::a {
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: Modification of posix namespace can result to undefined behavior [cert-msc53-cpp]
+}
+
+using namespace std;
+
+int main() {
+  A::B::b = 6;
+  A::B::c = 7;
+
+  return 0;
+}
+