DNS – Secure Network Resolver

emPSN in conjunction with JISC is able to offer schools and connected members the use of a Secure Network Resolver service sDNS.  

What is the Service

The service is a filtered DNS resolver that provides interception where the FQDN or Target IP is known to be compromised or a risk. The inclusive service can be used by all connected members. 

Clean service request – When the client makes a DNS request to a service that is clean (no reported security issues) the service will return the IP details like any standard DNS request. 

Dirty service request – When the client makes a DNS request to a service that has been compromised the service will return the IP details for the safe warning page / IP. Where this is a URL/Web Request the returned IP will be for a safe block page resource.

Example block page – http://bad-domain.soc.ja.net/  

When a member sees the block page, this is due to a FQDN or IP being intercepted by the service and referring the customer to a safe ip – the block page. 

This will happen where the resource is known to be or is known to have been compromised.  Once the FQDN/IP is effectively clean the service will return to normal operation.

False Positives or Block Page Queries 

In the event of a user seeing the RPZ block screen, it contains links to support@empsn.org.uk 

In order for the user to generate a false positive report. Clicking the link on the page populates a standard email message, alternatively we ask that you send the following information:

  • Client IP: 
  • Queried Domain  
  • Queried Port:  
  • URL:  
  • Time of Access(UTC):  
  • Commend 

Upon receipt of the request emPSN will assess the request to determine if this is a false positive or a user education matter.  We expect the actual number of false positives to be less than 0.5% of all blocks. 

For information on other DNS services from emPSN:

Should you require any further assistance on this and any other empsn services please contact us on support@empsn.org.uk

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