Important note about SSL VPN compatibility for 20.0 MR1 with EoL SFOS versions and UTM9 OS. Learn more in the release notes.

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Sophos Firewall blocking root DNS servers as Psiphon Proxy when using Unbound w/ AdGuard Home DNS

alan weir

When my at-home DNS server which is running running Unbound with Adguard Home DNS contacts the root DNS servers, the root servers are detected as psiphon proxy by the firewall. I do not have any Psiphon proxy app on any of my devices. Is this a false detection?

I have followed some tutorials on how to block proxies and tunnels, and Qname multiple DNS, ect. I have Psiphon Proxy as a blocked app in my application filter.

I am not sure what is causing this...here is a screenshot showing the Unbound contacting the root servers, and the root servers responding, and are blocked. The source IP address is from country Brunei.



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    it is possibly correct, because an IP check shows it as a VPN provider.

    Ian

    XG115W - v20.0.2 MR-2 - Home

    XG on VM 8 - v21 GA

    If a post solves your question please use the 'Verify Answer' button.

  • 0 in reply to rfcat_vk

    Ok, that is bizarre. I investigated some more and it seems that 202.93.214.163 is actually *NOT* one of the 13 root name servers that can be found on the internet. I'll have to do some more digging around. 

    Even stranger, before I switched to using the XG firewall I was using the UTM with the same setup, and the root servers were being detected as C&C servers and blocked by the Advanced Threat Detection. I am using TLS decryption on my DNS server which is running Ubuntu with Unbound configured, and it seems that TLS/SSL inspection is necessary to detect this Psiphon proxy/tunnel app.

    I might do a reinstall soon and just use a different distro that has less call-home features in it, like CentOS or plain old Debian. I also am alarmed that these Linux distros use plain HTTP update mirrors instead of HTTPS, where a MITM could occur during an update.

    I could go with Ubuntu server instead but I really want to avoid using SSH if I can....

  • 0 in reply to alan weir

    His Alan,

    SSL/TLS will not detect DNS because DNS uses UDP 53 and SSL/TLS at this stage cannot scan UDP.

    Ian

    XG115W - v20.0.2 MR-2 - Home

    XG on VM 8 - v21 GA

    If a post solves your question please use the 'Verify Answer' button.

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