diff --git a/src/net.h b/src/net.h
--- a/src/net.h
+++ b/src/net.h
@@ -448,6 +448,14 @@
     virtual void InitializeNode(const Config &config, CNode *pnode) = 0;
     virtual void FinalizeNode(const Config &config, NodeId id,
                               bool &update_connection_time) = 0;
+
+protected:
+    /**
+     * Protected destructor so that instances can only be deleted by derived
+     * classes. If that restriction is no longer desired, this should be made
+     * public and virtual.
+     */
+    ~NetEventsInterface() = default;
 };
 
 enum {
diff --git a/src/net_processing.h b/src/net_processing.h
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -26,8 +26,8 @@
  */
 static const unsigned int DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN = 100;
 
-class PeerLogicValidation : public CValidationInterface,
-                            public NetEventsInterface {
+class PeerLogicValidation final : public CValidationInterface,
+                                  public NetEventsInterface {
 private:
     CConnman *connman;
 
diff --git a/src/validationinterface.h b/src/validationinterface.h
--- a/src/validationinterface.h
+++ b/src/validationinterface.h
@@ -33,9 +33,25 @@
 
 class CValidationInterface {
 protected:
+    /**
+     * Protected destructor so that instances can only be deleted by derived
+     * classes. If that restriction is no longer desired, this should be made
+     * public and virtual.
+     */
+    ~CValidationInterface() = default;
+    /**
+     * Notifies listeners of updated block chain tip
+     *
+     * Called on a background thread.
+     */
     virtual void UpdatedBlockTip(const CBlockIndex *pindexNew,
                                  const CBlockIndex *pindexFork,
                                  bool fInitialDownload) {}
+    /**
+     * Notifies listeners of a transaction having been added to mempool.
+     *
+     * Called on a background thread.
+     */
     virtual void TransactionAddedToMempool(const CTransactionRef &ptxn) {}
     virtual void
     BlockConnected(const std::shared_ptr<const CBlock> &block,