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DNS Tunneling Attack

The Domain Name System (DNS), a broadly utilized and trusted component of the net, can be weaponized through a DNS tunneling assault. This escapade leverages this standard to bypass the target's privacy benchmarks and send malicious traffic through.

In order to fully exfiltrate stats and circumvent security standards, cybercriminals are making use of fraudulent domain names and DNS servers.

Let's talk a little bit more about DNS before we move into detailing what the DNS tunneling attack is and how it works.

DNS Tunneling Attack

An Overview DNS Tunneling

DNS is short for Domain Name System. It makes Internet use possible today. It adapts domain titles like into machine-friendly IP inscriptions like Regular purchasers don't have to recall complicated numbers. Instead, individuals are effortlessly remembering course titles and using them to navigate and discover their preferred news, athletic, or other websites.

Many resources use a constant DNS translation query. Because of this, DNS trade is trustworthy and extensively deployed. DNS was not considered a hazard to hostile transmissions and info exfiltration because it was simply created to resolve titles. However, DNS is more than a domain name translator. DNS requests can also transport small amounts of stats between gadgets, networks, and hosts. This makes DNS vulnerable to attacks.

Most corporations rarely check DNS packages for dubious activities. Rather, they analyze online and email traffic for potential assaults. DNS tunneling hazards can be prevented by closely overseeing each terminus.

How Does DNS Tunneling Works?

DNS channeling outbreaks use a client-server mechanism to tunnel spyware or info. Let's break down the procedure of how does DNS tunneling exfiltrate data.

The user downloads a bug, or a hacker exploits the device’s amenability to send an unwanted payload. Most fraudsters want to stay connected to the infected gadget to run instructions or exfiltrate info. Thus, the invader can establish C2. Traffic should clear via network perimeter security benchmarks and remain undetected until it intersects the target grid.

DNS works well for tunnel setup. Infosec utilizes the phrase for a standard association that goes through borderline privacy with a payload of info (mandate). DNS exfiltration attacks disguise content in DNS disputers and transfer them to a cybercriminal's server. DNS traffic travels easily past perimeter security mechanisms like gateways. The hacker creates a domain tag and establishes a reliable title hubspot for DNS exfiltration.

The virus or payload on the jeopardized gadget queries a DNS subdomain for concealed transmission. The attacker's server receives the DNS inquiry from the recursive DNS server. The hacked device receives fraudulent DNS facts with order info from the server. Consequently, the attack goes undetected.

The DNS Tunnelling outbreak can be broken down into the following stages:

  1. The hacker sets up a website by registering a domain name and directing it to a server it controls. There is malicious tunneling software preinstalled.
  2. The cybercriminal infects a device with malware and breaches the firewall of the victim. There are no restrictions on DNS requests passing through the barrier.
  3. The Recursive DNS server (DNS resolver) queries root and top-level domain servers for the IP address.
  4. The DNS resolver then forwards the DNS query to the attacker-controlled authoritative DNS server, which contains the tunneling software.
  5. Without warning, a connection is established between the cybercriminal and the victim.
How Does DNS Tunneling Works

DNS Tunneling-Related Attacks

The fact that the hackers typically don't intend to accomplish their aim while launching a DNS tunneling attack is one of the most important considerations to remember. A successful DNS tunneling attack is instead used as a springboard for further criminal activity. Furthermore, the actual DNS hijacking activity is not the first stage in the assault, unlike certain other methods of hacking.

It is best understood in the context of other types of malicious activity rather than as an end in itself. The following are examples of common attacks linked to DNS pivoting.


Attack TypeRelation to DNS Tunneling
Malware InstallationDNS redirecting attacks begin with this. These attacks can be avoided with proper virus and malware monitoring and elimination.
User Credential CollectionThe infected machine can collect user credentials and send them to the attacker via the DNS tunnel they control.
Network Foot printingDNS exfiltration gives hackers network foot printing data. It can also be exploited by additional malware deployed through the DNS encapsulation attack to make the destructive software more effective.
Data TheftHackers steal and spread sensitive data in several ways. The hacked DNS tunnel controls these methods.
Communication ControlAdvanced DNS hijacking toolkits regularly "check in" with the hacker's host server to receive commands. Hackers can act in the future by continuously checking in with the host server. These attacks are long-term threats that could last years.

DNS Tunneling Detection

Several methods exist for detecting DNS tunneling assault. However, there are two basic types that can be distinguished:

Payload Analysis

The DNS payload for one or more inquiries and responses will be evaluated for tunnel indications. 

  • Assessing request and response size

DNS data exfiltration utilities often include as much data as feasible in queries and responses. Tunneling requests have longer labels. Long names have up to 255 symbols and 63 symbols.

  • Confusing hostnames

DNS names with dictionary words are usually legitimate. Encoded names are generally out of order and use extra characters.

  • Data analysis

Checking DNS titles’ character staff can reveal tunneling. Credible DNS names have limited numbers. Inscribed titles have many numbers. The percentage of numerical typescripts in field names and the length of the Longest Meaningful Substring (LMS) may also aid.

  • Unusual DNS Records

Examine DNS archives that clients don't implement. Look at TXT records.

  • Infraction of a regulation

If a scheme necessitates all DNS lookups to go through an internal DNS server, noncompliance can be detected.

  • Unique impressions 

The DNS header can be parsed for concrete information using a signature. Now inspect the payload for the precise chapters.

Traffic Analysis

Over time, traffic patterns are analyzed.

  • IP address-wise DNS traffic volume

Checking the amount of DNS data that comes from a certain client IP label is a straightforward and easy thing to do.

  • Domain DNS traffic

Examining whether or not a specific domain name is receiving a great deal of traffic is another uncomplicated and fundamental procedure. Field name-based DNS tunnel utilizes tunnel data. All tunneled traffic is that domain name.

  • Domain hostnames

Every DNS tunneling request requires a hostname. That increases the amount remarkably compared to a conventional, reliable domain name.

  • DNS server geolocation

Inspect for a lot of DNS traffic going to places where you don't sell.

  • Domain archive 

A domain name's A record (AAAA archive) or NS record creation date can be checked. This method is excellent for uncovering domain titles that are being put to illicit use.

Examples of DNS Tunneling Attacks

This is a serious hazard to network safety, and there are various cases of DNS tunneling attack example that hackers can use to bypass privacy requirements, steal data or execute malicious code.

Direction And Management

An infected machine can spread malware by using a different method than TCP/UDP associations to transmit commands and collect data. From this vantage point, a variety of standard attacks are available to the intruder.

Information Extraction

It's possible to slowly leak particulars by encoding them in a series of DNS host searches.

Wlan Violence and Code Bypass

By taking advantage of services that enable outbound IP communication, a hacker can set up a full-fledged IPv4 tunnel. This permits them to enter a private grid without paying for access or dealing with the restrictions imposed by grid overseers.

How to Defend?

Although DNS is a necessary amenity for internet functionality, it is vital to address the privacy risks linked with DNS tunneling and implement benchmarks to block DNS tunneling while still ensuring the proper functioning of the service. Therefore, protecting yourself from DNS hijacking requires a multi-pronged approach.

  • Check and record suspicious IP inscriptions and domain names from unknown origins more closely.
  • All clients on the local network can be instructed to send their Domain Name System queries to a central DNS server. With this method, you can restrict access to potentially harmful websites.
  • It is crucial to continually be on the lookout for potentially malicious domain names, and DNS traffic monitoring is the best way to achieve this. In this way, the likelihood of a DNS covert channel attack is diminished.
  • Create a DNS firewall to detect and prevent intrusion by hackers.
  • Another great choice is a real-time DNS system that can identify out-of-the-ordinary DNS requests and DNS server traffic patterns.

Application Security and APIs With Wallarm

Wallarm API Security platform provides extensive defense for modern cloud-native APIs and legacy web apps from new and unknown attacks. Wallarm is the only solution that combines premium API security with forefront Web Application Firewall (WAAP) features, making it suited for securing a wide variety of APIs and web applications across various cloud deployments. Are you ready to secure your APIs? Take the free trial now.



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February 26, 2024
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