This page lists OSINT DNS RPZ Feeds for recursive resolvers to enhance security by blocking malware, phishing, and C2 domains. Submit your RPZ feed if it’s not listed.
Response Policy Zones(RPZ) or DNS Firewall or Protective DNS (thanks CISA) is a solid way to use the DNS protocol as a defense. For a primer on DNS RPZ, please see the blog post
While investigating a bit of oddity with the Skype app on Mac OS X, I wanted to capture all traffic from only the Skype processes.
But first, a little background on the issue. All DNS traffic from my systems is routed through a WireGuard tunnel. The peer endpoint at the other end runs a recursive resolver with DNS Response Policy Zones (DNS RPZ).
I’ve been running a WireGuard tunnel and routing DNS from my phone through a recursive resolver(unbound + rpz). Here are the battery stats.
Prior to WireGuard, an OpenVPN tunnel on the phone would drain the battery out in no time! pic.twitter.com/0rJVcJk1iq
The issue is – that as soon as the WireGuard tunnel is disabled, Skype will try connecting to Google DNS(8.8.8.8) and www.bing.com. Perhaps Skype bypasses the local recursive resolver set on the system and sends the DNS queries for its hosts to Google DNS directly? I cannot ascertain that yet, and it warrants a thorough investigation.
I was alerted to this by Little Snitch after I refreshed the rules. A ritual that I seem to follow every few months.
Little Snitch Network Monitor contains a hidden gem. The ability to capture traffic of a specific process.
For example, by right-clicking on any process, you should see the option to Capture Traffic. That should open a terminal window prompting for the sudo password.
After capturing traffic and interrupting should result in a PCAP on the Desktop. Neat!
Measuring ping and DNS from different vantage points using RIPE Atlas has been something that I have been using for some time now. You can read about installing a RIPE Atlas software probe here
A few weeks ago, I came across Shodan’s geoping and geodns API, which provides ping and DNS lookup from a few locations and other details such as RTT. This is great because you can quickly check ping and DNS resolution on systems where you only have curl running.
You always have the RIPE Atlas project for more detailed and sophisticated use-cases. To get started with the RIPE Atlas project, check the webinar I delivered some time ago for APNIC.
A couple of weeks ago, at my $dayjob, we implemented a recursive resolver with RPZ in an enterprise network.
After a few days, the customer got back to us with an issue – the DNS resolution of the domain esic.in failed with an NXDOMAIN response. After a cursory look at the problem, it became evident that esic.in resolved correctly but www.esic.in did not.
The customer also reported that if they switched the resolver to 8.8.8.8, the DNS resolution of www.esic.in was without any problems, and the website was accessible in the network.
So, what is causing the DNS issue with www.esic.in with the on-prem resolver?
Let’s find out. To start with the basics, here are the authoritative name servers of the domain esic.in,
$ whois esic.in | grep "Name Server:"
Name Server: ns-1089.awsdns-08.org
Name Server: ns-52.awsdns-06.com
Name Server: ns-1978.awsdns-55.co.uk
Name Server: ns-882.awsdns-46.net
If we traverse the DNS delegation from the root to esic.in, we get valuable insights,
. 518400 IN NS k.root-servers.net.
. 518400 IN NS l.root-servers.net.
. 518400 IN NS d.root-servers.net.
. 518400 IN NS e.root-servers.net.
. 518400 IN NS j.root-servers.net.
. 518400 IN NS b.root-servers.net.
. 518400 IN NS g.root-servers.net.
. 518400 IN NS a.root-servers.net.
. 518400 IN NS h.root-servers.net.
. 518400 IN NS m.root-servers.net.
. 518400 IN NS i.root-servers.net.
. 518400 IN NS c.root-servers.net.
. 518400 IN NS f.root-servers.net.
in. 172800 IN NS ns1.registry.in.
in. 172800 IN NS ns2.registry.in.
in. 172800 IN NS ns3.registry.in.
in. 172800 IN NS ns4.registry.in.
in. 172800 IN NS ns5.registry.in.
in. 172800 IN NS ns6.registry.in.
esic.in. 3600 IN NS ns-882.awsdns-46.net.
esic.in. 3600 IN NS ns-1978.awsdns-55.co.uk.
esic.in. 3600 IN NS ns-52.awsdns-06.com.
esic.in. 3600 IN NS ns-1089.awsdns-08.org.
esic.in. 300 IN A 115.113.201.36
esic.in. 300 IN A 218.248.15.136
esic.in. 172800 IN NS ns-1089.awsdns-08.org.
esic.in. 172800 IN NS ns-1978.awsdns-55.co.uk.
esic.in. 172800 IN NS ns-52.awsdns-06.com.
esic.in. 172800 IN NS ns-882.awsdns-46.net.
And, here is the delegation trace from the root to www.esic.in,
. 518400 IN NS a.root-servers.net.
. 518400 IN NS e.root-servers.net.
. 518400 IN NS c.root-servers.net.
. 518400 IN NS b.root-servers.net.
. 518400 IN NS m.root-servers.net.
. 518400 IN NS l.root-servers.net.
. 518400 IN NS h.root-servers.net.
. 518400 IN NS j.root-servers.net.
. 518400 IN NS d.root-servers.net.
. 518400 IN NS g.root-servers.net.
. 518400 IN NS i.root-servers.net.
. 518400 IN NS k.root-servers.net.
. 518400 IN NS f.root-servers.net.
in. 172800 IN NS ns1.registry.in.
in. 172800 IN NS ns4.registry.in.
in. 172800 IN NS ns5.registry.in.
in. 172800 IN NS ns6.registry.in.
in. 172800 IN NS ns3.registry.in.
in. 172800 IN NS ns2.registry.in.
esic.in. 3600 IN NS ns-882.awsdns-46.net.
esic.in. 3600 IN NS ns-1089.awsdns-08.org.
esic.in. 3600 IN NS ns-1978.awsdns-55.co.uk.
esic.in. 3600 IN NS ns-52.awsdns-06.com.
www.esic.in. 3600 IN NS lbr1.esic.in.
www.esic.in. 3600 IN NS lbr2.esic.in.
www.esic.in. 0 IN A 218.248.15.136
If you compare the two outputs and look closely, the authoritative nameservers have delegated www.esic.in to the name servers lbr1.esic.in and lbr2.esic.in
And at the time of the issue, the nameservers lbr1.esic.in and lbr2.esic.in did not respond to Do53(UDP) resulting in an NXDOMAIN!
DNSViz also reported the non-responsive nameservers as well as OpenDNS cachecheck,
At the time of writing this blog post, the name servers lbr1.esic.in. and lbr2.esic.in. were responding and www.esic.in was resolving correctly. But for more than 24+ hours, they were unresponsive resulting in some random people on the Internet in India being unable to access the website.
I presented on how we at my $dayjob do Threat Hunting using DNS at APNIC 52.
This is the same presentation I gave at SANOG 37, but luckily, I had the full quota of 20 minutes to complete the presentation without rushing into it.
I had the opportunity to present on Hyperlocal root and the LocalRoot project at sdns://2021 last week
I’ve written and presented about Hyperlocal root aka RFC 8806 in the past. In the context of privacy, Hyperlocal root does provide a possible solution to the problem,
Prevent snooping by third parties of requests sent to DNS root servers
RFC8806
Aside from that, faster negative responses to non-existent domains eliminates junk to the root
I did a quick check with Google Chrome 92.0.4515.131 and oddly enough I am still seeing this behaviour,
Aug 16 09:03:24 unbound[1:0] info: 192.168.100.4 ckgydztukkdsta. A IN
Aug 16 09:03:24 unbound[1:0] info: 192.168.100.4 lubdcupibujjne. A IN
Aug 16 09:03:24 unbound[1:0] info: 192.168.100.4 ltvlataieb. A IN
This will need further researching and debugging which I will save for another post.
A big thank you to Frank for organising sdns://2021 and also to folks from Quad9 for their help.
For some reason as can be seen in the video, presentation is stuck at a specific slide, the PDF can be found here
At SANOG 37, I had the opportunity to share some of the ways in which we have been doing Threat Hunting using DNS at my $dayjob.
Here is the video of the presentation.
I also had a little demo but I decided to improvise and add slides instead, since the program was running a little behind schedule and I was the only one standing between everyone and their lunch. trouble was also lurking.
That aside, the same paper ‘Threat Hunting using DNS’ has been accepted at APNIC 52 and hopefully, I will be able to demo the juicy bits.
tl;dr If Jio VoWiFi isn’t working for you, set a different DNS resolver on the phone. While I am a big proponent of running your own resolver in the network, ( runyourownresolver.in ) , you could test by using open resolvers. The issue doesn’t seem to be impacting everyone and only a subset of users.
To begin with, there are multiple things broken in the authoritative name servers ns1.vowifi.jio.com. and ns2.vowifi.jio.com. of vowifi.jio.com which I’ll cover a bit later.
I came across reports ( See here & here ) of Jio VoWiFi not working for many and while the reports were sketchy, I decided to test this myself.
Below is a snippet from a log file of a dns query to vowifi.jio.com from my phone(192.168.1.137) to a recursive resolver(Unbound) which I run in my network,
May 28 15:54:35 root unbound: [1300:0] info: 192.168.1.137 vowifi.jio.com. A IN
Ideally, the domain is standardised & is made up of Mobile Network Code(MNC) and Mobile Country Code(MCC). For example – in the case of Airtel VoWiFi, the domain name that I see hitting my Unbound resolver is epdg.epc.mnc045.mcc404.pub.3gppnetwork.org. where MNC – 045 and MCC – 404 which signifies Airtel – Karnataka region.
However, oddly enough, Reliance Jio seems to be using vowifi.jio.com. Having said that, the standardised domain name works as well. For example – epdg.epc.mnc861.mcc405.pub.3gppnetwork.org. resolves to 49.44.59.36 and 49.44.59.38
Below is the dns resolution entire delegation chain. From my home network, I can see that the vowifi.jio.com resolves to 49.44.59.38 and 49.44.59.36
. 518400 IN NS a.root-servers.net.
. 518400 IN NS b.root-servers.net.
. 518400 IN NS c.root-servers.net.
. 518400 IN NS d.root-servers.net.
. 518400 IN NS e.root-servers.net.
. 518400 IN NS f.root-servers.net.
. 518400 IN NS g.root-servers.net.
. 518400 IN NS h.root-servers.net.
. 518400 IN NS i.root-servers.net.
. 518400 IN NS j.root-servers.net.
. 518400 IN NS k.root-servers.net.
. 518400 IN NS l.root-servers.net.
. 518400 IN NS m.root-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
jio.com. 172800 IN NS ns1.jio.com.
jio.com. 172800 IN NS ns2.jio.com.
jio.com. 172800 IN NS ns3.jio.com.
jio.com. 172800 IN NS ns4.jio.com.
vowifi.jio.com. 3600 IN NS ns1.vowifi.jio.com.
vowifi.jio.com. 3600 IN NS ns2.vowifi.jio.com.
vowifi.jio.com. 5 IN A 49.44.59.38
vowifi.jio.com. 5 IN A 49.44.59.36
At this point, I confirmed that VoWiFi on Jio works by putting the phone on Airplane mode while remain connected to WiFi. A ~22 minute call worked flawlessly.
To confirm that vowifi.jio.com was indeed the domain name that needs to resolve for VoWiFi to work on Jio, I configured an entry for vowifi.jio.com to return a NXDOMAIN answer in my DNS RPZ aka DNS Firewall in Unbound.
With that configured, any DNS query for vowifi.jio.com from any device in the network will be meted out with a NXDOMAIN answer. Below is a snippet from the Unbound log confirming the RPZ rule applied.
May 28 17:31:50 root unbound: [1191:0] info: 192.168.0.137 vowifi.jio.com. A IN
May 28 17:31:50 root unbound: [1191:0] info: RPZ applied [custom block to test vowifi] vowifi.jio.com. nxdomain 192.168.0.137@64521 vowifi.jio.com. A IN
;; ->>HEADER<<- opcode: QUERY, rcode: NXDOMAIN, id: 14747
;; flags: qr aa rd ra ; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;; vowifi.jio.com. IN A
;; ANSWER SECTION:
;; AUTHORITY SECTION:
;; ADDITIONAL SECTION:
;; Query time: 136 msec
;; SERVER: 192.168.0.250
;; WHEN: Thu May 28 18:03:42 2020
;; MSG SIZE rcvd: 32
In the context of VoWiFi, the other noticeable problems with DNS infrastructure of Jio –
A/AAAA records for ns1.vowifi.jio.com, ns2.vowifi.jio.com are missing
ns1.vowifi.jio.com(49.44.59.6), ns2.vowifi.jio.com(49.44.59.7) don’t respond to queries over TCP
The other interesting thing that is worth observing is that when you try resolving vowifi.jio.com from outside India or use a DNS resolver which is perhaps not geographically located within India, the authoritative name servers ns1.vowifi.jio.com(49.44.59.6), ns2.vowifi.jio.com(49.44.59.7) give out a different set of IP addresses – 49.45.63.1, 49.45.63.2
; <<>> DiG 9.16.3 <<>> @127.0.0.1 vowifi.jio.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13728
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;vowifi.jio.com. IN A
;; ANSWER SECTION:
vowifi.jio.com. 4 IN A 49.45.63.1
vowifi.jio.com. 4 IN A 49.45.63.2
;; Query time: 352 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Sat May 30 06:23:23 IST 2020
;; MSG SIZE rcvd: 75
To confirm this hypothesis, I decided to utilise the RIPE Atlas probes to run a measurement. If you’re unaware of the RIPE Atlas project, check an earlier post – Host a RIPE Atlas software probe in your network.
And the results of the measurement are interesting. Out of the 75 probes which participated in the measurement, there were many probes which received the response 49.45.63.1 & 49.45.63.2 to the DNS query to vowifi.jio.com
ASN
AS Name
DNS Response 1
DNS Response 2
Resolver IP address
4758
NICNET-VSNL-BOARDER-AP National Informatics Centre, IN’
49.45.63.2
49.45.63.1
164.100.3.1
4758
NICNET-VSNL-BOARDER-AP National Informatics Centre, IN’
49.45.63.1
49.45.63.2
164.100.3.1
24186
RAILTEL-AS-IN RailTel Corporation of India Ltd., Internet Service Provider, New Delhi, IN’
TATACOMM-AS TATA Communications formerly VSNL is Leading ISP, IN’
49.45.63.1
49.45.63.2
8.8.8.8
16509
AMAZON-02, US’
49.44.59.38
49.44.59.36
::1
15169
GOOGLE, US’
49.45.63.1
49.45.63.2
::1
139331
DCORP-AS-AP DevelentCorp., IN’
49.44.59.36
49.44.59.38
::1
24309
CABLELITE-AS-AP Atria Convergence Technologies Pvt. Ltd. Broadband Internet Service Provider INDIA, IN’
49.45.63.2
49.45.63.1
192.168.1.10
9498
BBIL-AP BHARTI Airtel Ltd., IN’
49.45.63.1
49.45.63.2
192.168.139.245
internationalvowifi.jio.com also seems to indicate VoWiFi International calling, which resolves to 49.44.59.36 and 49.44.59.38 from my vantage point. The same resolves to 49.45.63.1 and 49.45.63.2 from every location that I’ve managed to check from outside India.
Looking at the results, most likely the issue is with how ns1.vowifi.jio.com & ns2.vowifi.jio.com are responding to client subnet (EDNS0) in DNS queries.
Update (06/08/2020) – APNIC has published this post on their blog. Robbie Mitchell from APNIC was of great help in correcting a few things and polishing the article. You can read the Part 1 on the APNIC blog here
DNS(Domain Name System) is the crucial & ubiquitous fabric of the Internet. While on the surface, users rely on accessing websites, apps, email etc underneath it’s the DNS database which provides the map for the Internet.
It’s fair to say that everything on the Internet begins with a DNS query. This means that the DNS is used for legitimate purposes and as well as abused by bad actors.
Adding a layer of security to a flat network
In the context of COVID-19, where most of us are working from home, security of the the devices & data being accessed from a hostile home network has become a major talking point over the last couple of months. The home network is atypical from an enterprise network from a security perspective and apart from its inherent flaws, it’s a flat network.
A flat network is a computer networkdesign approach that aims to reduce cost, maintenance and administration.[1] Flat networks are designed to reduce the number of routers and switches on a computer network by connecting the devices to a single switch instead of separate switches. Unlike a hierarchical network design, the network is not physically separated using different switches.
The topology of a flat network is not segmented or separated into different broadcast areas by using routers.
Here is a representation of a flat network design,
The constraints of a flat network are,
No segmentation of traffic – Single broadcast domain
Easy & rapid propagation of malicious traffic within the network
One of the layers of security that can be brought into a flat network at an economical cost is by leveraging DNS. Before we look into how that can be implemented, here is a DNS primer for what happens when a domain name is accessed in a network,
Shift of the recursive resolvers
In the above diagrammatic representation, the part which is doing the most heavy lifting is the Recursive DNS Server or Recursive resolver. At the very beginning of the Internet, users themselves ran recursive resolvers on the machines or in the network. This model slowly shifted to the network operators (ISP’s) offering this as a bundled, free of cost offering along with the service. And the model has moved DNS resolution further away from the user with the advent of the Cloud/Quad DNS providers. To name a notable few, Google Public DNS (8.8.8.8, 8.8.4.4), Cloudflare (1.1.1.1, 1.0.0.1), Quad9(9.9.9.9) etc.
While each of these open resolvers services promote faster dns resolution, in reality they are still further away from the user from a round trip metric. Even though all of these open resolver services use IP Anycast, the proximity to the user cannot compete with a local resolver. In obvious terms, the recursive resolver which is in the users network or even the resolver provided by the Internet Service Provider will always be closest.
The one definitive advantage that the cloud/quad DNS open resolvers provide is the availability of a large cache.
If you aren’t convinced yet on running your own DNS resolver instead of outsourcing it to the cloud/quad DNS providers, I would urge you to read Why should I run my own DNS resolver?
And most importantly, if you want to leverage DNS Response Policy Zones (DNS Firewall) to add a layer of security in your network, you need to run a recursive resolver.
What is DNS Response Policy Zones(RPZ) ?
It’s currently an Internet-draft and not a standard yet. The latest draft is available here
Allows policy to be applied to DNS queries. Set a differentiated route for the bad domains
Economical solution – a RaspberryPi can act as recursive resolver with DNS RPZ for the entire network – especially useful & low cost solution for home networks, SOHO etc
Just like the functioning of a firewall, RPZ is made up of TRIGGERS & ACTIONS.
This is all good but without threat intelligence data, a DNS Firewall doesn’t add any value.
Threat intelligence RPZ feeds
While there are many threat intelligence providers which provide a DNS RPZ feed, below are some of the free/community ones,
While this is not something new, it perhaps has more significance because of the ever increasing market share of more than 60% of Chromium based browsers.
Chromium based browsers have a very uncanny method to check if the web browser is sitting behind a captive portal. And if you’re running a recursive resolver in your network with a large user base running Chromium based browsers (Google Chrome, Brave etc), it might even startle you if you observe the recursive resolver logs.
Here is a snippet from my unbound resolver as soon as I start Google Chrome on the machine(192.168.0.188),
Jun 3 11:16:31 root unbound: [1283:0] info: 192.168.0.188 pwpsfrn. A IN
Jun 3 11:16:31 root unbound: [1283:0] info: 192.168.0.188 yeytluindg. A IN
Jun 3 11:16:31 root unbound: [1283:0] info: 192.168.0.188 zkgtcrxrpfjcjxr. A IN
A research project at USC What’s In A Name? goes into some detail with the classification.
Here is the summary of the study,
Though the root server system handles this application-specific load sufficiently, it is clear that Chrome’s trick of using randomly generated names to discover whether it’s behind a captive portal contributes significantly to the traffic received at the root zone.