What is the technique employed by John to bypass the firewall?

John, a professional hacker, decided to use DNS to perform data exfiltration on a target network, in this process, he embedded malicious data into the DNS protocol packets that even DNSSEC cannot detect. Using this technique. John successfully injected malware to bypass a firewall and maintained communication with the victim machine and C&C server.

What is the technique employed by John to bypass the firewall?
A . DNS cache snooping
B . DNSSEC zone walking
C . DNS tunneling method
D . DNS enumeration

View Answer

Answer: C

Explanation:

DNS tunneling may be a method wont to send data over the DNS protocol, a protocol which has never been intended for data transfer. due to that, people tend to overlook it and it’s become a well-liked but effective tool in many attacks. Most popular use case for DNS tunneling is obtaining free internet through bypassing captive portals at airports, hotels, or if you are feeling patient the not-so-cheap on the wing Wi-Fi. On those shared internet hotspots HTTP traffic is blocked until a username/password is provided, however DNS traffic is usually still allowed within the background: we will encode our HTTP traffic over DNS and voilà, we’ve internet access. This sounds fun but reality is, browsing anything on DNS tunneling is slow. Like, back to 1998 slow. Another more dangerous use of DNS tunneling would be bypassing network security devices (Firewalls, DLP appliances…) to line up an immediate and unmonitored communications channel on an organisation’s network. Possibilities here are endless: Data exfiltration, fixing another penetration testing tool… you name it. To make it even more worrying, there’s an outsized amount of easy to use DNS tunneling tools out there. There’s even a minimum of one VPN over DNS protocol provider (warning: the planning of the web site is hideous, making me doubt on the legitimacy of it). As a pentester all this is often great, as a network admin not such a lot.

How does it work: For those that ignoramus about DNS protocol but still made it here, i feel you deserve a really brief explanation on what DNS does: DNS is sort of a phonebook for the web, it translates URLs (human-friendly language, the person’s name), into an IP address (machine-friendly language, the phone number). That helps us remember many websites, same as we will remember many people’s names.

For those that know what DNS is i might suggest looking here for a fast refresh on DNS protocol, but briefly what you would like to understand is:

• A Record: Maps a website name to an IP address.example.com? 12.34.52.67

• NS Record (a.k.a. Nameserver record): Maps a website name to an inventory of DNS servers, just in case our website is hosted in multiple servers.example.com? server1.example.com, server2.example.com Who is involved in DNS tunneling?

• Client. Will launch DNS requests with data in them to a website.

• One Domain that we will configure. So DNS servers will redirect its requests to an outlined server of our own.

• Server. this is often the defined nameserver which can ultimately receive the DNS requests.

The 6 Steps in DNS tunneling (simplified):