Showing results for 
Show  only  | Search instead for 
Did you mean: 

Web Gateway: Configuring SSL Tap with Network Data Loss Prevention (NDLP) Monitor


In the McAfee Web Gateway 7.7.1 release, you can now direct decrypted HTTPS traffic to a TAP interface on the MWG appliance. From this interface, other devices, such as DLP solutions, IPS solutions and Advanced Threat Protection solutions can inspect the decrypted traffic for monitoring and analysis purposes. This document provides an example of how to configure the SSL TAP functionality on MWG to send decrypted SSL traffic to a McAfee NDLP Monitor 9.3.4 system.

Reference Topology

An example topology used in this example is depicted below:





Web Gateway Configuration


Network Interface Configuration

In this example, the MWG is configured as an Explicit Proxy, listening on port 9090 on the Internal Network using network interface eth0. The SSL TAP will be configured to direct the decrypted traffic to a second interface, eth1, that will be dedicated for use as a private TAP network.

When MWG copies the decrypted packets to this interface we will configure the SSL TAP such that the packets retain their original Client IP Address, which enables the originator to be identified by NDLP Monitor. As a result, we don’t need to assign an IP address to this interface.

In the MWG UI, navigate to Configuration -> Appliances -> Network Interfaces, select the eth1 interface, select the checkbox to enable the interface and then select Disable IPv4 under IP Settings in the IPv4 tab:



If the MWG is configured to support IPv6 traffic, then repeat this step under the IPv6 tab.



SSL Tap Interface Configuration

The SSL Tap Interface configuration allows you to specify to which interface the decrypted packets are copied. More than one interface can be configured if required.

For each interface, you can configure the following settings:

    • Client IP for IPv4 Traffic: This specifies the IPv4 Address used as the Client IP Address when the decrypted packets are copied and sent on this interface. If not specified, then the original Client IP address in the HTTPS request received by the MWG will be used (equivalent to the MWG Client.IP property).
    • Client IP for IPv6 Traffic: As above but for IPv6 traffic.
    • Client MAC: This specifies the MAC Address used when the decrypted packets are copied and sent on this interface. If not specified, then the MAC address of the SSL TAP interface is used.


In this example, the SSL TAP will be configured such that the packets retain their original Client IP Address, which enables the originator to be identified by NDLP Monitor.


In the MWG UI, navigate to Configuration > Appliances > SSL Tap, enable the SSL Tap functionality and add the eth1 interface, leaving the Client IP and MAC address fields blank:



In a MWG cluster, this should be repeated on each MWG appliance.



Enable SSL Tap Event

Once the SSL Tap Interface is configured, the actual copying of the decrypted traffic to the interface is enabled by calling the ‘Enable SSL Tap’ event in a rule.

Calling this event from a rule allows you to control exactly which request/responses are copied to the SSL Tap interface. For example, you might choose to call this Event from a Rule that uses one of more Criteria, such as a URL Destination, a URL Category or a specific group of Users.

In this example, the SSL TAP will be enabled for all SSL traffic.

In the MWG UI, navigate to Policy -> Rule Sets -> SSL Scanner, and add the ‘Enable SSL Tap’ event to the Enable Content Inspection rule in the Content Inspection ruleset:



Note, for reasons that should be obvious, SSL Content Inspection is a prerequisite for using the SSL Tap functionality.



Network DLP Monitor Configuration


Capture Interface Configuration

Each NDLP Monitor appliance has two capture ports: eth2 and eth3. In this example, eth2 is connected to the same private TAP network that was configured above.

Ordinarily, a NDLP Monitor port is designed to ‘sniff’ for traffic on the network and therefore requires that it be connected to a switch port that has Promiscuous mode enabled.

However, when the MWG copies packets to the SSL Tap interface it sets the destination MAC address of the packets to the Broadcast MAC address (ff:ff:ff:ff:ff:ff) and as a result, the NDLP Monitor capture port will receive those packets directly without requiring Promiscuous mode to be enabled on the switch port.




Once the SSL Tap is configured, you can use the tcpdump packet capture utility on either the MWG or on the NDLP Monitor appliance to confirm that packets are being copied to the SSL Tap interface.

The Wireshark trace below shows an example of a Packet Capture run on the Private TAP Network showing the decrypted packets that have been copied for a HTTPS Request to

Note that that the Client IP address of the highlighted request is, which is the IP Address of the client workstation in this example and that the destination MAC address is the Broadcast Address.


>>> Example Capture Download <<<

capture download.png



DLP Incidents

Once traffic is being captured by NDLP Monitor, you can configure Policies and Rules to trigger Incidents when specific criteria are met, e.g. sensitive information being uploaded to specific websites.

The screenshots below show an example Rule, which is configured to trigger an Incident when the keyword ‘lorem’ is detected in an HTTP_POST to the site and the resultant incident.


image6.png image7.png



Optional Configuration


McAfee Logon Collector

By configuring the SSL Tap on MWG to use the original Client IP when packets are copied to the SSL Tap interface, NDLP Monitor can identify the originating computer that sent the request. But, by default it has no direct knowledge of which user was logged into that computer at the time.

McAfee Logon Collector is designed to address this by collecting information from Active Directory and other sources, and mapping the IP Address of a computer back to the user who is logged onto it.

NDLP Monitor supports integration with McAfee Logon Collector and enables the User Information to be determined and displayed along with the Incident:




To configure McAfee Logon Collector, please refer to the McAfee Logon Collector Installation Guide and also follow the instructions in the Connect McAfee Logon Collector to McAfee DLP section of the McAfee Network DLP Product Guide. Failing to configure the necessary certificate authentication between the two will result in failure to retrieve the user details from McAfee Logon Collector.

Labels (1)

small pictures.

small pictures.jpg


Sorry about that, I noticed that as I was cleaning it up. I'll get some new screenshots done.


All fixed now.


Jon, good morning!

Thank you

Version history
Revision #:
3 of 3
Last update:
‎04-03-2018 09:18 AM
Updated by:

Community Help Hub

    New to the forums or need help finding your way around the forums? There's a whole hub of community resources to help you.

  • Find Forum FAQs
  • Learn How to Earn Badges
  • Ask for Help
Go to Community Help

Join the Community

    Thousands of customers use the McAfee Community for peer-to-peer and expert product support. Enjoy these benefits with a free membership:

  • Get helpful solutions from McAfee experts.
  • Stay connected to product conversations that matter to you.
  • Participate in product groups led by McAfee employees.
Join the Community
Join the Community