NXDOMAIN Hijacking in .ph: When Unregistered Domains Become a Brand Risk

In digital risk protection, suspicious domains are often assessed through a familiar lens: typosquatting, phishing, fake login pages, malicious redirects, or broader brand abuse. In many cases, that model is correct.

However, a recent investigation involving a .ph domain highlighted a different class of issue, one that is easy to misinterpret if the analysis stops at the webpage level.

In this case, the core risk was not a registered phishing site controlled by an attacker. Instead, the behaviour appeared to be driven by TLD-level wildcard DNS or NXDOMAIN substitution, causing unregistered domain names to resolve and redirect users to third-party content.

That distinction matters. It changes how the incident should be classified, investigated, and communicated to stakeholders.

The Trigger: Suspicious .ph Domains Resembling a Client Brand

The investigation began with a domain under the .ph country-code top-level domain that resembled a client's brand. At first glance, it looked like a conventional brand abuse case.

The domain did not consistently host a fixed phishing page. Instead, it behaved more like a traffic redirection point:

• sometimes landing on generic advertising content
• sometimes redirecting onward to third-party destinations
• in certain cases, leading to high-risk content such as gambling or adult websites

That behaviour naturally raises concern. But the decisive finding came from the registration check.

The domain was not registered.

Under normal DNS behaviour, an unregistered domain should return NXDOMAIN, indicating that the name does not exist. That was not what happened here.

Instead, the domain resolved to a live IP address:

This immediately shifted the investigation from a simple domain abuse review to a broader infrastructure analysis.

What Was Actually Happening

In a healthy DNS model, when a user requests an unregistered name, the resolver should ultimately receive an authoritative response indicating non-existence. That negative response is fundamental to how internet naming works.

In this case, however, unregistered .ph names appeared to behave differently:

• they did not return NXDOMAIN
• they resolved to a common IP address
• subsequent web requests triggered redirect behaviour
• observed patterns included redirect scripts such as /page/bouncy.php
• encoded parameters suggested downstream forwarding logic and campaign tracking

In practical terms, a domain that should not exist was being made to look active.

This is commonly described as NXDOMAIN hijacking.

That label is widely understood, but from a technical standpoint it is slightly imprecise. A more rigorous description is:

That framing better reflects what appears to be happening: the TLD infrastructure substitutes the expected non-existent-domain response with a wildcard resolution, and the resulting traffic is then redirected or monetised downstream.

Why the Distinction Matters

If analysts focus only on the final webpage, they may reach the wrong conclusion.

A quick review could lead to statements such as:

• the suspicious domain is a live phishing asset
• the domain has been registered by an attacker
• a standard takedown process should be initiated

But if the domain is not registered, and multiple random unregistered names under the same TLD resolve in a similar way, the problem is different in nature.

The more accurate interpretation is often:

• the specific brand-like domain is unregistered
• the observed resolution is driven by TLD-level wildcarding or response substitution
• downstream content is reached through redirect logic rather than attacker-controlled domain ownership
• the issue should be assessed as infrastructure-level brand risk, not automatically as a confirmed hosted phishing asset

This distinction is critical for evidence quality, reporting accuracy, and client trust.

Is “NXDOMAIN Hijacking” the Right Term?

The term is acceptable in common industry use, and it is helpful for broad communication.

James Wade's article, The Wild World of NXDOMAIN Hijacking in 2023: Wildcard DNS in Action, documents similar behaviour across several TLDs and specifically notes that .ph may resolve unregistered names to 45.79.222.138. That external reference aligns closely with the behaviour observed in this case.

However, in a formal technical report, it is better to qualify the term. A stronger formulation would be:

That phrasing preserves accessibility without weakening technical accuracy.

Why This Matters for Brand Owners

This is not just an obscure DNS curiosity. It can create real business impact.

1. Brand Erosion

A user may type a brand-like .ph domain and be taken to gambling, adult, or otherwise unsafe content. Even if the brand never owned the domain and the domain was never registered, the user may still associate that experience with the brand.

2. Investigation Errors

Many detection workflows assume that an unregistered domain will return NXDOMAIN. When a TLD does not follow that behaviour, automated tools and manual analysts may incorrectly classify the case as a malicious hosted website.

3. Compliance and Stakeholder Pressure

For regulated sectors such as financial services, healthcare, and payments, brand-like domains resolving to inappropriate content can trigger difficult internal questions:

• Why was this not detected earlier?
• Does this represent an unmanaged external digital risk?
• Is the business expected to take enforcement action?
• Does this indicate a failure in brand monitoring?

Without careful technical framing, the resulting report may overstate or misstate the actual issue.

4. Misaligned Response Strategy

If the event is treated as a conventional phishing domain, teams may spend time pursuing the wrong actions. In many cases, the more useful task is to confirm the registration status, validate the DNS pattern, document the redirect chain, and classify the issue correctly.

Likely Commercial Drivers

Why would this behaviour exist at all?

Two explanations are commonly relevant.

Traffic Monetisation

Requests that should terminate in a non-existent-domain response are instead redirected toward pages that can generate advertising or referral value.

Defensive Registration Pressure

If a brand owner sees that its name under a given TLD can lead to unsafe content, the business may feel compelled to register the domain defensively, even though the name was previously unregistered. In effect, the surrounding ecosystem turns non-existent names into a source of commercial pressure.

Recommended Investigation Approach

For brand protection and security teams, the key lesson is simple: do not stop at the webpage.

A defensible workflow should include the following steps.

1. Confirm Whether the Domain Is Actually Registered

Do not infer ownership from browser behaviour alone. Check authoritative sources and registrar-side indicators where possible.

2. Test Multiple Random Unregistered Names

If several obviously unregistered names under the same TLD resolve to the same IP or exhibit similar redirect behaviour, that strongly suggests a TLD-wide pattern rather than a domain-specific malicious deployment.

3. Compare DNS Behaviour Across Resolvers

Where appropriate, review results from multiple resolvers and inspect authoritative behaviour as closely as possible. This helps separate local resolver artefacts from actual zone-level behaviour.

4. Capture the Full Redirect Chain

The final page is only part of the evidence. Preserve:

• the original request
• intermediate redirects
• script paths
• key parameters
• final destinations
• timing and repeatability observations

5. Separate Content Risk from Domain Control

Unsafe final content may still be present, but that does not automatically mean the suspicious brand-like domain is a registered attacker asset.

6. Use Accurate Incident Language

If the evidence shows an unregistered domain resolving through wildcard DNS and redirecting through shared infrastructure, the case is better described as:

• infrastructure-level brand exposure
• registry wildcard DNS behaviour
• NXDOMAIN substitution with downstream redirect activity
• brand and trust risk arising from TLD-level behaviour

That language is far more defensible than simply declaring a confirmed phishing domain.

Cyberoo's Technical View

From a security operations and digital risk perspective, the most important takeaway is this:

Sometimes the observed behaviour comes from the infrastructure around the domain rather than the domain itself.

That may seem like a subtle distinction, but in practice it affects:

• how risk is classified
• what enforcement actions are justified
• how evidence is documented
• how management and clients interpret the finding
• whether the response is proportionate and technically sound

For mature digital risk protection, this level of technical discrimination is not optional. It is part of producing reliable, high-quality intelligence.

Closing Perspective

The case examined here is a useful reminder that the unused space of the internet is not always empty.

A brand-like domain may be unregistered, yet still resolve, redirect, and expose users to content that damages trust. That makes this more than a DNS oddity. It is a real brand, customer, and reporting problem.

For brand protection, cyber threat intelligence, and digital risk teams, the lesson is clear: