Receiving a Netbios Vulnerability alert

Last updated: February 2, 2017

You may have recently received a letter and/or email from Virgin Media explaining that we have been notified that a device on your network has a vulnerability known as an open NetBIOS. If you have received such a communication from us, please follow the advice given on this page to resolve the issue.

Overview

NetBIOS is used to share files and folders across a local network. Other applications can use NetBIOS to map a network, allowing them to send messages to destination computers. Ports commonly used by NetBIOS can be exploited to commit abuse when exposed to the wider Internet.

What has happened?

We work with a number of not-for-profit organisations across the banking industry and security sectors that collate information on devices across the Internet that appear to be compromised or misconfigured. This means that your compromised or misconfigured device is publicly accessible on the Internet, and therefore the scanning that is performed by these organisations is not within your private network.

We suspect a device connected to your home network may have an open NetBIOS vulnerability.

For more information on these reports please visit netbiosscan.shadowserver.org*

If the settings are left open they can be exploited to unwittingly participate in malicious activities, for example a Distributed Denial of Service (DDoS) attack.

It is therefore important that you follow the advice in this article. **
 

What can I do about it?

We're here to help and if you have a basic knowledge of computers and connected devices there are a number of steps you can take to secure home network.

To resolve this issue, please follow the steps below.

Virgin Media Hub 3.0

To close the vulnerable port on the Virgin Media Hub 3.0:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Security on the left side of the page
  • Select the Port Forwarding option
  • Remove any rules that will keep ports 135, 137 & 139 open
  • Select the Port Triggering option
  • Remove any rules that will keep ports 135, 137 & 139 open

Virgin Media Super Hub:

To close the vulnerable port on the Super Hub 1 or 2’s firewall:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Advanced Settings and accept the prompt
  • Scroll down to the Security section
  • Select the Port Forwarding option
  • Remove any rules that will keep ports 135, 137 & 139 open
  • Click the Apply option
  • Select the Port Triggering option
  • Tick the Delete box next to any rules that will keep ports 135, 137 & 139 open
  • Click the Apply option

3rd party routers

If you use a 3rd party router in conjunction with the Virgin Media Super Hub or Hub 3.0, your router's firewall will need to be configured to ensure ports 135, 137 and 139 are not accessible outside of your local network - this can be performed by blocking the port or removing any Port Forwarding rules for that port. In order to identify how to do this with your particular router, refer to the documentation for your device or refer to the manufacturer's website.

It is important to check all your devices sit behind a firewall. In most cases your firewall is configured as a part of your router, this is the case with the Virgin Media Superhub and Hub 3.0. If you have specifically disabled the Firewall in your router, it is crucial that you configure your devices to sit behind a firewall that blocks ports 135, 137 and 139. If this does not apply to you, please proceed to the next step.

Modem Mode - If you are using your Virgin Media Super Hub or Hub 3.0 in Modem Only mode, it is essential that you are using a firewall on any device or router that is plugged directly into the Hub. When in Modem Only mode, your Hub does not operate with a firewall. If this does not apply to you, please proceed to the next step.

DMZ - Most firewalls, including the one provided with the Virgin Media Super Hub and Hub 3.0 include a DMZ option. This feature allows for a device using a specific local IP address on your home network (e.g. 192.168.0.2) to bypass your Firewall settings. This is occasionally necessary if you are using a device that has its own firewall configured. If you have a device configured in your firewall's DMZ that does not use its own firewall, it is crucial that you disable this option immediately. Computers operating without a firewall are extremely vulnerable to attack as all ports are essentially exposed to the wider Internet.

To check if a device is configured in the DMZ on your Virgin Media Super Hub 1 or 2:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Advanced Settings
  • Select DMZ
  • To remove a device from the DMZ, uncheck the tick box at the top of the page

To check if a device is configured in the DMZ on your Virgin Media Hub 3.0:

  • Access your Hub's configuration page - default web address: 192.168.0.1
  • Login with your username and password, default will be shown on the Hub itself
  • Select Security on the left side of the page
  • Select the DMZ option
  • To remove a device from the DMS, tick the Disable box

Where can I find further information and advice?

If you’d like further advice then our forum community will be happy to help. Just visit virginmedia.com/community and join the conversation on our Security Matters board.

You can find general security advice and articles on other vulnerabilities by checking Security Hub at virginmedia.com/securityhub

*These links to external sites are provided as a courtesy and we are not responsible for the content of these sites or any problems encountered whilst applying these steps and we are not able to provide any technical support for such problems.

** These fixes are provided as a courtesy and we are not responsible for any problems encountered whilst applying these steps and we are not able to provide any technical support for such problems.


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