diff --git a/src/modelfuzz/rules.py b/src/modelfuzz/rules.py
index e2b7aef..c4706b0 100644
--- a/src/modelfuzz/rules.py
+++ b/src/modelfuzz/rules.py
@@ -154,11 +154,17 @@ def _check_recursive(self, data: object) -> Violation | None:
                         reason=f"String contains sensitive keyword: '{keyword}'",
                     )
         elif isinstance(data, dict):
-            for value in data.values():
+            for key, value in data.items():
+                violation = self._check_recursive(key)
+                if violation:
+                    return violation
+
                 violation = self._check_recursive(value)
                 if violation:
                     return violation
-        elif isinstance(data, (list, tuple)):
+        elif isinstance(data, (bytes, bytearray)):
+            return self._check_recursive(data.decode("utf-8", errors="ignore"))
+        elif isinstance(data, (list, tuple, set, frozenset)):
             for item in data:
                 violation = self._check_recursive(item)
                 if violation:
diff --git a/tests/test_rules.py b/tests/test_rules.py
index 389dcd4..d267e2f 100644
--- a/tests/test_rules.py
+++ b/tests/test_rules.py
@@ -246,3 +246,33 @@ def test_allows_clean_data(self, filter: SensitiveDataFilter):
         data = {"user": "alice", "action": "login"}
         violation = filter(data)
         assert violation is None
+
+    def test_blocks_sensitive_dict_key(self, filter: SensitiveDataFilter):
+        """Ensure it blocks sensitive keywords in dictionary keys."""
+        violation = filter({"api_key": "abc123"})
+        assert violation is not None
+        assert "api_key" in violation.reason
+
+    def test_blocks_sensitive_bytes(self, filter: SensitiveDataFilter):
+        """Ensure bytes are inspected."""
+        violation = filter(b"contains password")
+        assert violation is not None
+        assert "password" in violation.reason
+
+    def test_blocks_sensitive_bytearray(self, filter: SensitiveDataFilter):
+        """Ensure bytearrays are inspected."""
+        violation = filter(bytearray(b"contains api_key"))
+        assert violation is not None
+        assert "api_key" in violation.reason
+
+    def test_blocks_sensitive_set(self, filter: SensitiveDataFilter):
+        """Ensure sets are inspected."""
+        violation = filter({"contains secret"})
+        assert violation is not None
+        assert "secret" in violation.reason
+
+    def test_blocks_sensitive_frozenset(self, filter: SensitiveDataFilter):
+        """Ensure frozensets are inspected."""
+        violation = filter(frozenset({"contains password"}))
+        assert violation is not None
+        assert "password" in violation.reason