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Open DNS resolver vulnerability alert

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 DNS Resolver. If you have received such a communication from us, read the advice given on this page to help resolve the issue. Note: This article is intended to provide advice. Virgin Media is not responsible for any issues encountered in the course of resolving the issue and is not able to provide any technical support for such problems.


The Domain Name System (DNS) is a system used by computers to convert domain names to an IP address on the Internet. A DNS server is a system that accepts requests from other computer systems to convert domains to IP addresses.

An open recursive DNS Resolver is a DNS server that has been opened up to answer DNS queries from any computer system on the Internet. If configured incorrectly, these servers can be exploited to unwittingly participate in malicious activities.

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 DNS resolver vulnerability.

For more information on these reports please visit*

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. **

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 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

* links to external sites are provided as a courtesy and virgin media is not responsible for the content of these sites or any issues encountered as a result of  applying information from these sites. Virgin media 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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