diff --git a/p2pool/dash/stratum.py b/p2pool/dash/stratum.py
index 365df882..c5ea8c5e 100644
--- a/p2pool/dash/stratum.py
+++ b/p2pool/dash/stratum.py
@@ -72,8 +72,20 @@ def rpc_submit(self, worker_name, job_id, extranonce2, ntime, nonce):
             bits=x['bits'],
             nonce=pack.IntType(32).unpack(getwork._swap4(nonce.decode('hex'))),
         )
-        return got_response(header, worker_name, coinb_nonce)
-    
+        res = got_response(header, worker_name, coinb_nonce)
+
+        # Disconnect miners with large DOA rates to prevent DoS
+        if len(self.wb._inner.my_share_hashes) > 20:
+            if float(len(self.wb._inner.my_doa_share_hashes)) / float(len(self.wb._inner.my_share_hashes)) > 0.60:
+                self.transport.loseConnection()
+
+        # Disconnect miners with large hash > target to prevent DoS
+        if self.wb._inner.total_hashes > 20:
+            if float(self.wb._inner.invalid_hashes) / float(self.wb._inner.total_hashes) > 0.05:
+                self.transport.loseConnection()
+
+        return res
+
     def close(self):
         self.wb.new_work_event.unwatch(self.watch_id)
 
diff --git a/p2pool/work.py b/p2pool/work.py
index 1a6637ee..aa5b7460 100644
--- a/p2pool/work.py
+++ b/p2pool/work.py
@@ -50,6 +50,9 @@ def __init__(self, node, my_pubkey_hash, donation_percentage, merged_urls, worke
         self.my_share_hashes = set()
         self.my_doa_share_hashes = set()
 
+        self.invalid_hashes = 0
+        self.total_hashes = 0
+
         self.address_throttle = 0
 
         self.tracker_view = forest.TrackerView(self.node.tracker, forest.get_attributedelta_type(dict(forest.AttributeDelta.attrs,
@@ -477,10 +480,13 @@ def _(err):
 
                 self.share_received.happened(dash_data.target_to_average_attempts(share.target), not on_time, share.hash)
 
+            self.total_hashes += 1
+
             if pow_hash > target:
                 print 'Worker %s submitted share with hash > target:' % (user,)
                 print '    Hash:   %56x' % (pow_hash,)
                 print '    Target: %56x' % (target,)
+                self.invalid_hashes += 1
             elif header_hash in received_header_hashes:
                 print >>sys.stderr, 'Worker %s submitted share more than once!' % (user,)
             else: