Tag Archive for: TDM to SIP

Why Spam Calls Still Happen: From Number Spoofing to Modern Fraud Prevention

A few times a week, most of us still get that call from an unknown number, making us wonder whether we should answer or not. It is most likely spam, yet there is always a small chance it could be important. For businesses, ignoring such calls is not an option.

Some calls are flagged as “possible spam,” which makes them easy to ignore. Others slip through unnoticed, blending in with legitimate traffic.

So why, after years of regulatory efforts, new technologies, and stronger network security, do spam calls continue to be such a persistent problem?

Let’s take a closer look at how spam actually happens and the tools that service providers are using to keep it under control.

How Voice Fraud Scaled with IP Networks

Fraud in telecom used to be a more hands-on operation. In the past, every call originated from a physical line tied to a physical location. Gaining access took effort, and scaling any kind of fraudulent activity was difficult.

That changed with the arrival of IP-based voice. Today, large volumes of calls can be generated automatically, routed globally, and disguised through caller ID spoofing or the misuse of unallocated and recycled numbers. Fraud no longer depends on physical access to the network, but rather on automation and weaknesses in verification.

The problem is not the phone number itself but how easily it can be impersonated. Fraudsters exploit the fact that the global numbering system was designed for connectivity, not identity verification. As a result, calls can appear legitimate at first glance, even when they are being injected into the network by untrusted or unknown sources.

Why Phone Numbers Still Matter

Despite the rise of IP messaging, video calls, and app-to-app communication, phone numbers remain the foundation of global voice networks.

When you call a restaurant, a courier, or a bank, you are using that universal addressing system. Businesses depend on it because it works across every device, carrier, and country. That is why over-the-top options like WhatsApp or FaceTime, while useful, still rely on the telephone number or operate within closed ecosystems that cannot replace the universal reach of the public voice network.

The problem is that not every number in the network is in use. Some are unassigned, some are inactive, and some exist in grey zones between carriers. These conditions create a perfect opportunity for spoofing.

Understanding Spoofing and the Challenge of Trust

When a spammer “spoofs” a number, they are effectively pretending to be someone they are not. The call might appear to come from a familiar area code, a local business, or even a valid toll-free number.

Because voice networks were designed to prioritize connectivity rather than caller verification, a spoofed number can travel across carriers and borders without immediate detection. The result is spam calls that look completely legitimate—at least until you answer.

And, as mentioned earlier, while individual users can ignore a suspicious call, businesses cannot. A customer support team cannot afford to let calls go unanswered, even if some turn out to be fraudulent or part of a scam attempt. That is one of the reasons the problem remains so persistent.

The Tools Fighting Back

The good news is that the telecom industry is far from idle. There is a growing ecosystem of solutions designed to verify, validate, and, when necessary, block suspicious calls before they reach the end user.

  1. Do-Not-Originate (DNO) Lists
    DNO databases catalog numbers that should never originate calls, such as toll-free numbers that are meant only to receive inbound calls or unallocated number ranges. If a call shows up from one of those numbers, the network can simply prevent it from going through.
  2. STIR/SHAKEN
    STIR/SHAKEN allows originating carriers to digitally sign calls, certifying that the calling party is authorized to use the number. The signature travels with the call, giving downstream networks a way to assess trust before connecting it. Coverage is not yet universal, and not every call path supports it, but it is a big step forward in verifying caller identity.
  3. Blacklists
    Blacklists have been around for years, cataloging known spam or fraud numbers. But maintaining them is resource-intensive, and stale entries can lead to false positives, where legitimate calls end up being blocked. That is why many service providers now use curated, vendor-maintained databases or dynamic systems that flag patterns rather than just individual numbers.
  4. Analytics and AI
    Pattern recognition and analytics tools are beginning to supplement the older, static approaches. By monitoring calling behavior—things like volume, frequency, location, and duration—networks can detect anomalies in real time. However, these systems are difficult to implement at scale. Large call centers, for example, can resemble spam in traffic patterns even when perfectly legitimate, such as calling people during an election cycle. It is a powerful tool, but one that requires careful calibration.

The Role of Service Providers

Fraud prevention starts at the network edge. Service providers have the first opportunity to evaluate whether a call looks legitimate. By combining number validation, attestation, and policy enforcement, they can dramatically reduce the flow of fraudulent traffic.

Session Border Controllers (SBCs) play an important role here. SBCs serve as the gatekeepers for traffic entering and leaving the network. They can perform checks against DNO databases, verify signatures, apply routing policies, and log the results for auditing.

It is about making fraud prevention an integrated function of call handling.

The Path Forward

Spam calls are not going away overnight, but the tools to fight them are improving. The key is a layered approach that combines foundational measures like DNO and STIR/SHAKEN with smart policy enforcement and data-driven analytics.

The real progress happens when service providers work together, sharing information, aligning on standards, and ensuring that every step in the call path takes responsibility for trust.

Want the Full Conversation?

For a deeper dive into how spam calls persist, why phone numbers remain central to fraud prevention, and how tools like STIR/SHAKEN and DNO are changing the game, check out our latest TelcoBridges Podcast episode with Luc Morissette. We unpack the patterns behind spam calls and explore what service providers can do right now to keep them off the network. Listen to the episode.

 

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Network Modernization in Emerging Markets: Common Goals, Different Roadblocks

Telecom modernization is no longer a question of “if,” but “how soon.”

Across the globe, operators are moving their voice networks from circuit-switched TDM to packet-based IP.
In emerging markets like Africa and Latin America, this shift carries even more weight. These regions are some of the fastest-growing mobile and broadband markets in the world. Brazil alone has more than 200 million mobile subscribers. Growth at this scale puts tremendous pressure on operators to expand voice and data services quickly, securely, and cost-effectively.

The challenge?

Traditional TDM systems weren’t built to scale at today’s pace. That’s why modernization in these regions is both urgent and complex: a balancing act between upgrading to IP and maintaining reliability for millions of subscribers.

Let’s look at three of the most common roadblocks operators face, and how they’re finding ways forward.

Roadblock #1: Budget Pressures

Every operator must manage costs, but when capital has to stretch across large territories with limited infrastructure, and rapidly growing subscriber bases, tough choices are inevitable. In such cases, investments in less flexible and expensive legacy voice systems are harder to justify.

And it’s not just about the hardware budget. Time is an equally important factor. Complex customization and integration work can drain scarce engineering resources. Solutions that are designed to integrate with existing infrastructure using standard interfaces and more straightforward configuration require less effort to deploy and interconnect, and reduce dependence on scarce legacy expertise.

Roadblock #2: Fraud Exposure

Fraud is a universal problem, but its impact depends heavily on local regulations. In countries where frameworks are strong and unified, countermeasures can be applied consistently. Brazil’s adoption of STIR/SHAKEN is a recent example, driven by the sharp rise in spam and fraudulent calls.

In markets where regulations are still fragmented, fraudsters often find more room to exploit gaps. For operators growing quickly in these environments, the challenge is clear: secure networks that are growing rapidly while working within uneven or still-shifting regulatory protections.

Roadblock #3: Legacy Realities

Despite the global push toward IP, legacy systems remain essential. Copper and TDM are still in place in many regions, and they won’t disappear overnight. Operators need to extend the life of these assets while keeping them interoperable with modern SIP environments.

Flexible, cost-efficient gateways are proving critical here. By deploying gateways closer to subscribers in regions where TDM is predominant, operators can convert calls from TDM to SIP at the network edge. This reduces the distance where expensive copper lines are required, lowering costs while still ensuring reliable voice services.

IMS: Defining the Core of Modernization

One of the most important enablers of modernization — in both emerging and established markets — is IMS (IP Multimedia Subsystem).

IMS isn’t just about voice. It’s a standardized framework that allows different types of services (voice, video calling, messaging, presence, and more) to interconnect cleanly across networks. For voice specifically, IMS provides the foundation that enables mobile and fixed-line networks to interoperate, while still supporting essential functions such as emergency calling.

In practice, IMS offers two big advantages:

  • Modularity: Operators can add or replace components without disrupting the whole system.

  • Interoperability: Clear specifications make it easier for equipment from different vendors to work together.

Session Border Controllers (SBCs) play a vital role in this architecture. Acting as secure interfaces to IMS cores, SBCs help operators manage interoperability, enforce policies, and maintain the scalability and flexibility needed to align with global standards.

The Balance Between Old and New

For operators in emerging markets, modernization is rarely a clean break. It’s about protecting existing investments while preparing for what’s next. That means:

  • Maintaining installed bases with certified, supported equipment.
  • Enabling interconnection with rapidly expanding mobile networks.
  • Supporting voice services across both fixed and mobile environments.
  • Adding fraud protection at every layer — because threats target both old and new infrastructure.

The goal isn’t to abandon the past or leap recklessly into the future, but to balance between both.

Moving Forward Together

While every market has its own challenges, the destination is the same: reliable, secure, and interoperable voice services in an IP-first world.

Emerging markets like Mexico, Brazil, India, and South Africa may face tighter budgets, heavier reliance on legacy systems, and greater fraud exposure. But these pressures also create urgency and spark innovation in how modernization is achieved.

At TelcoBridges, we see this first-hand with our partners and customers worldwide. Whether through ProSBC for IP scaling and fraud protection, or Tmedia gateways for efficient legacy integration, our role is to provide solutions that make modernization achievable without requiring disruptive, all-at-once upgrades.

The good news? With the right mix of efficient solutions, every operator can stay on course of keeping voice reliable, secure, and fully interoperable.

Example: Paratus

Paratus, a pan-African operator active in multiple countries, faced the challenge of expanding services cost-effectively while working within infrastructure constraints. By deploying TelcoBridges SBCs and media gateways, they were able to interconnect reliably and migrate to SIP without disrupting customers.

For more details, read the full Paratus Case Study.

Want the Full Conversation?

For a deeper dive into how modernization is playing out across growing regions, from the pressures of budgets and fraud to the role of IMS and legacy integration, check out our latest podcast episode.

 

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