diff --git a/SignalServiceKit/src/Messages/OWSBlockingManager.h b/SignalServiceKit/src/Messages/OWSBlockingManager.h
index 2c2892580..0c2720626 100644
--- a/SignalServiceKit/src/Messages/OWSBlockingManager.h
+++ b/SignalServiceKit/src/Messages/OWSBlockingManager.h
@@ -31,6 +31,7 @@ extern NSString *const kNSNotificationName_BlockListDidChange;
 - (void)removeBlockedGroupId:(NSData *)groupId;
 
 - (BOOL)isRecipientIdBlocked:(NSString *)recipientId;
+- (BOOL)isGroupIdBlocked:(NSData *)groupId;
 - (BOOL)isThreadBlocked:(TSThread *)thread;
 
 - (void)syncBlockList;
diff --git a/SignalServiceKit/src/Messages/OWSMessageDecrypter.m b/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
index 94d2efec7..b8c9b7a79 100644
--- a/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
+++ b/SignalServiceKit/src/Messages/OWSMessageDecrypter.m
@@ -80,7 +80,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 #pragma mark - Blocking
 
-- (BOOL)isEnvelopeBlocked:(SSKProtoEnvelope *)envelope
+- (BOOL)isEnvelopeSenderBlocked:(SSKProtoEnvelope *)envelope
 {
     OWSAssert(envelope);
 
@@ -121,7 +121,7 @@ NS_ASSUME_NONNULL_BEGIN
         DDLogInfo(@"%@ decrypting envelope: %@", self.logTag, [self descriptionForEnvelope:envelope]);
 
         OWSAssert(envelope.source.length > 0);
-        if ([self isEnvelopeBlocked:envelope]) {
+        if ([self isEnvelopeSenderBlocked:envelope]) {
             DDLogInfo(@"%@ ignoring blocked envelope: %@", self.logTag, envelope.source);
             failureBlock();
             return;
diff --git a/SignalServiceKit/src/Messages/OWSMessageManager.m b/SignalServiceKit/src/Messages/OWSMessageManager.m
index 8358d6475..a24e60379 100644
--- a/SignalServiceKit/src/Messages/OWSMessageManager.m
+++ b/SignalServiceKit/src/Messages/OWSMessageManager.m
@@ -158,13 +158,30 @@ NS_ASSUME_NONNULL_BEGIN
 
 #pragma mark - Blocking
 
-- (BOOL)isEnvelopeBlocked:(SSKProtoEnvelope *)envelope
+- (BOOL)isEnvelopeSenderBlocked:(SSKProtoEnvelope *)envelope
 {
     OWSAssert(envelope);
 
     return [_blockingManager isRecipientIdBlocked:envelope.source];
 }
 
+- (BOOL)isDataMessageBlocked:(SSKProtoDataMessage *)dataMessage envelope:(SSKProtoEnvelope *)envelope
+{
+    OWSAssert(dataMessage);
+    OWSAssert(envelope);
+
+    if (dataMessage.group) {
+        return [self.blockingManager isGroupIdBlocked:dataMessage.group.id];
+    } else {
+        BOOL senderBlocked = [self isEnvelopeSenderBlocked:envelope];
+
+        // If the envelopeSender was blocked, we never should have gotten as far as decrypting the dataMessage.
+        OWSAssert(!senderBlocked);
+
+        return senderBlocked;
+    }
+}
+
 #pragma mark - message handling
 
 - (void)processEnvelope:(SSKProtoEnvelope *)envelope
@@ -184,7 +201,7 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     OWSAssert(envelope.source.length > 0);
-    OWSAssert(![self isEnvelopeBlocked:envelope]);
+    OWSAssert(![self isEnvelopeSenderBlocked:envelope]);
 
     switch (envelope.type) {
         case SSKProtoEnvelopeTypeCiphertext:
@@ -343,6 +360,16 @@ NS_ASSUME_NONNULL_BEGIN
     OWSAssert(dataMessage);
     OWSAssert(transaction);
 
+    if ([self isDataMessageBlocked:dataMessage envelope:envelope]) {
+        NSString *logMessage = [NSString stringWithFormat:@"Ignoring blocked message from sender: %@", envelope.source];
+        if (dataMessage.group) {
+            logMessage =
+                [logMessage stringByAppendingString:[NSString stringWithFormat:@" in group: %@", dataMessage.group.id]];
+        }
+        DDLogError(@"%@", logMessage);
+        return;
+    }
+
     if (dataMessage.hasTimestamp) {
         if (dataMessage.timestamp <= 0) {
             DDLogError(@"%@ Ignoring message with invalid data message timestamp: %@", self.logTag, envelope.source);