client.go       |  2 +-
 dht/announce.go | 14 ++++++++++++++
 dht/dht.go      | 14 ++++++++++++++

diff --git a/client.go b/client.go
index 465f10629d82698a3a9e7d2679266537ddd20c2e..dc5b66fd921b1ad7340a08e8a0fe7c995b9312f0 100644
--- a/client.go
+++ b/client.go
@@ -226,7 +226,7 @@ 	}
 	fmt.Fprintf(w, "Peer ID: %+q\n", cl.peerID)
 	if cl.dHT != nil {
 		dhtStats := cl.dHT.Stats()
-		fmt.Fprintf(w, "DHT nodes: %d (%d good)\n", dhtStats.Nodes, dhtStats.GoodNodes)
+		fmt.Fprintf(w, "DHT nodes: %d (%d good, %d banned)\n", dhtStats.Nodes, dhtStats.GoodNodes, dhtStats.BadNodes)
 		fmt.Fprintf(w, "DHT Server ID: %x\n", cl.dHT.ID())
 		fmt.Fprintf(w, "DHT port: %d\n", addrPort(cl.dHT.Addr()))
 		fmt.Fprintf(w, "DHT announces: %d\n", dhtStats.ConfirmedAnnounces)
diff --git a/dht/announce.go b/dht/announce.go
index 75a9558e643779cafc4986faa547de335ba02c7e..3b9dc32f3e0fad94eaedf3d5900f5acf4d6b16d1 100644
--- a/dht/announce.go
+++ b/dht/announce.go
@@ -108,6 +108,12 @@ 	}
 	if me.server.ipBlocked(addr.UDPAddr().IP) {
 		return
 	}
+	me.server.mu.Lock()
+	if me.server.badNodes.Test([]byte(addr.String())) {
+		me.server.mu.Unlock()
+		return
+	}
+	me.server.mu.Unlock()
 	me.contact(addr)
 }
 
@@ -162,6 +168,14 @@ 		}
 		me.mu.Unlock()
 
 		if vs := m.Values(); vs != nil {
+			for _, cp := range vs {
+				if cp.Port == 0 {
+					me.server.mu.Lock()
+					me.server.badNode(addr)
+					me.server.mu.Unlock()
+					return
+				}
+			}
 			nodeInfo := NodeInfo{
 				Addr: t.remoteAddr,
 			}
diff --git a/dht/dht.go b/dht/dht.go
index ed544f6066163216b9bca3497cf78682f76c96e7..5db6adb4c236d3e44811d2d29b46b6ef29fecd0e 100644
--- a/dht/dht.go
+++ b/dht/dht.go
@@ -22,6 +22,7 @@ 	"time"
 
 	"github.com/anacrolix/missinggo"
 	"github.com/anacrolix/sync"
+	"github.com/tylertreat/BoomFilters"
 
 	"github.com/anacrolix/torrent/bencode"
 	"github.com/anacrolix/torrent/iplist"
@@ -50,6 +51,7 @@ 	mu               sync.Mutex
 	closed           chan struct{}
 	passive          bool // Don't respond to queries.
 	ipBlockList      *iplist.IPList
+	badNodes         *boom.BloomFilter
 
 	numConfirmedAnnounces int
 	bootstrapNodes        []string
@@ -81,6 +83,8 @@ 	// Transactions awaiting a response.
 	OutstandingTransactions int
 	// Individual announce_peer requests that got a success response.
 	ConfirmedAnnounces int
+	// Nodes that have been blocked.
+	BadNodes uint
 }
 
 // Returns statistics for the server.
@@ -95,6 +99,7 @@ 	}
 	ss.Nodes = len(s.nodes)
 	ss.OutstandingTransactions = len(s.transactions)
 	ss.ConfirmedAnnounces = s.numConfirmedAnnounces
+	ss.BadNodes = s.badNodes.Count()
 	return
 }
 
@@ -121,6 +126,7 @@ 	}
 	s = &Server{
 		config:      *c,
 		ipBlockList: c.IPBlocklist,
+		badNodes:    boom.NewBloomFilter(1000, 0.1),
 	}
 	if c.Conn != nil {
 		s.socket = c.Conn
@@ -790,6 +796,9 @@ 	}
 	if !s.config.NoSecurity && !n.IsSecure() {
 		return
 	}
+	if s.badNodes.Test([]byte(addrStr)) {
+		return
+	}
 	s.nodes[addrStr] = n
 	return
 }
@@ -1214,3 +1223,8 @@ 		ret = append(ret, idNodes[id.ByteString()])
 	}
 	return ret
 }
+
+func (me *Server) badNode(addr dHTAddr) {
+	me.badNodes.Add([]byte(addr.String()))
+	delete(me.nodes, addr.String())
+}