diff --git a/lib/installer-exclude/jain-sdp.jar b/lib/installer-exclude/jain-sdp.jar
index 60eb51197..7275bb25b 100644
Binary files a/lib/installer-exclude/jain-sdp.jar and b/lib/installer-exclude/jain-sdp.jar differ
diff --git a/lib/installer-exclude/jain-sip-ri.jar b/lib/installer-exclude/jain-sip-ri.jar
index 1011fd54c..16e093a85 100644
Binary files a/lib/installer-exclude/jain-sip-ri.jar and b/lib/installer-exclude/jain-sip-ri.jar differ
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java b/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
index 001f28614..c724dca79 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
@@ -904,6 +904,15 @@ public void processRequest(RequestEvent requestEvent)
     {
         Request request = requestEvent.getRequest();
 
+        if(getRegistrarConnection() != null
+           && !getRegistrarConnection().isRegistrarless()
+           && !getRegistrarConnection().isRequestFromSameConnection(request))
+        {
+            logger.warn("Received request not from our proxy, ignoring it! "
+                + "Request:" + request);
+            return;
+        }
+
         // test if an Event header is present and known
         EventHeader eventHeader = (EventHeader)
             request.getHeader(EventHeader.NAME);
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/SipRegistrarConnection.java b/src/net/java/sip/communicator/impl/protocol/sip/SipRegistrarConnection.java
index 771c4457c..6b9d3a84d 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/SipRegistrarConnection.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/SipRegistrarConnection.java
@@ -15,6 +15,7 @@
 import javax.sip.header.*;
 import javax.sip.message.*;
 
+import gov.nist.javax.sip.message.*;
 import net.java.sip.communicator.service.protocol.*;
 import net.java.sip.communicator.service.protocol.event.*;
 import net.java.sip.communicator.util.*;
@@ -136,6 +137,20 @@ public class SipRegistrarConnection
      */
     private String registrationTransport = null;
 
+    /**
+     * We remember the last received address that REGISTER OK is coming from.
+     * For security reasons if we are registered this is the address
+     * that all messages must come from.
+     */
+    private InetAddress lastRegisterAddressReceived = null;
+
+    /**
+     * We remember the last received port that REGISTER OK is coming from.
+     * For security reasons if we are registered this is the port
+     * that all messages must come from.
+     */
+    private int lastRegisterPortReceived = -1;
+
     /**
     * Creates a new instance of this class.
     *
@@ -458,6 +473,11 @@ public void processOK(ClientTransaction clientTransatcion,
                 }
             }
 
+            // remember the address and port from which we received this
+            // message
+            lastRegisterAddressReceived =
+                    ((SIPMessage)response).getRemoteAddress();
+            lastRegisterPortReceived = ((SIPMessage)response).getRemotePort();
 
             //schedule a reregistration.
             scheduleReRegistration(scheduleTime);
@@ -482,6 +502,28 @@ && getRegistrationState().equals(RegistrationState.REGISTERING))
         }
     }
 
+    /**
+     * Checks a particular request is it coming from the same proxy we are
+     * currently using. A check for security reasons, preventing injection
+     * of other messages in the PP.
+     * @param request the request to check.
+     * @return <tt>false</tt> if the request doesn't belong to our register
+     *         or if we cannot decide we keep the old behaviour.
+     */
+    public boolean isRequestFromSameConnection(Request request)
+    {
+        SIPMessage msg = (SIPMessage)request;
+
+        if(msg.getRemoteAddress() != null
+            && lastRegisterAddressReceived != null)
+        {
+            if(!msg.getRemoteAddress().equals(lastRegisterAddressReceived)
+                || msg.getRemotePort() != lastRegisterPortReceived)
+                return false;
+        }
+        return true;
+    }
+
     /**
     * Sends a unregistered request to the registrar thus ending our
     * registration.
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/SipStackSharing.java b/src/net/java/sip/communicator/impl/protocol/sip/SipStackSharing.java
index 0636df2a0..79abd67ca 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/SipStackSharing.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/SipStackSharing.java
@@ -880,6 +880,25 @@ private ProtocolProviderServiceSipImpl findTargetFor(Request request)
                     }
                 }
 
+                // Let narrow candidates by checking addresses and ports
+                Iterator<ProtocolProviderServiceSipImpl> iterPP =
+                        candidates.iterator();
+                while(iterPP.hasNext())
+                {
+                    ProtocolProviderServiceSipImpl candidate = iterPP.next();
+
+                    if(!candidate.getRegistrarConnection().isRegistrarless()
+                        && !candidate.getRegistrarConnection()
+                            .isRequestFromSameConnection(request))
+                        iterPP.remove();
+                }
+
+                if(candidates.size() == 0)
+                {
+                    logger.error("no listeners, or message not fo us");
+                    return null;
+                }
+
                 // Past this point, our guess is not reliable. We try to find
                 // the "least worst" match based on parameters like the To field