DNS Sinkhole: Its Role in Cybersecurity – GreenCloud

People these days are very comfortable clicking on links on websites. This trend is a boon for criminals who create and distribute a ridiculous number of malicious URLs. Infected links can automatically download malware to your device or lead to fake websites that trick you into sharing sensitive information. This is clearly a threat to organizations whose ability to ensure data security contributes greatly to their success. A DNS loophole is a way to intercept malicious URLs in a way that targets the entire network rather than individual endpoints.

What is a DNS Sinkhole?

A DNS sinkhole is a cybersecurity technique that combats and neutralizes malicious online activities. It functions by intercepting and forwarding Domain Name System (DNS) queries, which are essential for translating human-readable domain names into IP addresses. Think of your home with locks on the doors to keep your home safe. Likewise, computers and networks need to be protected from bad things happening online. This is where the DNS hole comes in. It's like a digital lock that stops bad things from entering your network.

When you want to access a website, your browser asks the DNS server to find the address of that website. A DNS hole is like a sentinel at the entrance. Checks if the website you are trying to visit is safe. If it is not safe, the guard sends you to another address so that you do not accidentally end up in a dangerous place.

How does it work?

A DNS hole is relatively simple to operate, but the cyber security implications are powerful. Here's the step-by-step breakdown:

• Catch: When a request is made to access a domain from within the network, the DNS slot may intercept the request if the domain is known to be malicious.
• Redirect: Instead of letting the request go to a potentially malicious domain, the DNS sinkhole redirects it. This redirect can lead to a harmless IP address, essentially a dead end, or a server managed by network administrators for further analysis.
• Defense: As a result, any device within the protected network is prohibited from connecting to sites known to host malware, phishing scams, or other cyber threats, thereby protecting the integrity and security of the network.

Options for DNS Sinkhole implementation

Administrators have three options for adding a DNS sink to query chains.

• Relying on a third-party service as a DNS forwarder
• Setting up and configuring a private DNS server
• Using a firewall with a sinkhole feature

The easiest method is to outsource to a third-party service with hole capabilities. Administrators lose some customization options, but it takes the shortest time to install and secure. There are also no maintenance costs and you don't have to compile a personal list of dangerous domains.

However, if control is important to your operations, setting up your own DNS server is not the worst option. Someone knowledgeable should be willing to troubleshoot and analyze logs for a security investigation.

Instead of integrating a new service into your operations, you can pull similar effects from your existing firewall. You can use the firewall support options to troubleshoot and configure a database of domains for forwarding. The risk with this option is that if the firewall goes down, the hole goes down with it, while a separate service would act as an unnecessary security measure.

DNS hole limitations

There are several limitations associated with DNS sinkholes.

In order to block the malware or its traffic using a DNS loophole, the malware requires exploiting the organization's DNS server itself. Malware with its own hard-coded DNS server and IP address cannot be detected by the DNS loophole mechanism. However, this drawback can be mitigated by using perimeter firewalls configured to block all other outgoing DNS queries, but not the organization's DNS servers.

A DNS hole cannot prevent malware from executing and spreading to other computers. Also, malware cannot be removed from an infected machine using a DNS hole.

A DNS slot will be set with malware indicators and these indicators should be analyzed beforehand. Also, there may be false positives in malicious IP information collected from open sources that should be fed into a DNS sink. Sources may contain non-malicious URLs and therefore result in unwanted restriction to legitimate websites.

The DNS hole must be isolated from the external network so that the attacker is not aware of the fact that their C&C traffic is being throttled. Otherwise, it has the opposite effect, where attackers can manipulate the entries in the DNS hole and use them for malicious purposes.

DNS records should be implemented with “Time-to-Live” (TTL) parameters with short values, otherwise this may result in users caching old data for longer periods of time.

The result

A DNS socket is a smart way to use the existing DNS protocol to extend protection capabilities. Even if the malware becomes active on systems on your network, this strategy often prevents the malware from accomplishing its malicious purpose by preventing it from reaching the command and control server.

DNS holes allow administrators to preemptively block traffic to malicious domains by redirecting traffic to the hole rather than to the malicious destination. It offers a step against malware and acts as an additional layer of defense for the network.