Illegal VoIP: What is it? How to Detect and Prevent It?

Updated on: 3 Jul, 2024
Illegal VoIP: What is it? How to Detect and Prevent It?

Voice over Internet Protocol (VoIP) is the most popular way of carrying out business communication. It enables communication over voice, video, and multimedia using internet connectivity. VoIP eliminates the need for a public switched telephone network (PSTN). Therefore, it makes it difficult for authority bodies such as the police to trace such calls. In such cases, Illegal VoIP comes into existence.

Illegal VoIP activities have increased over time. In 2021, Delhi’s cyber cell busted a racket that used illegal VoIP to generate more than 2 lakhs calls in a day from the Gulf countries. VoIP can serve as a mask for miscreants to execute criminal or unlawful activities such as kidnapping, spying, etc. In short, it is of utmost importance to detect and prevent illegal VoIP.

Why is illegal VoIP on the rise?

Digital technology has evolved over the years, facilitating different spheres of life. Like other advancements, communication has also become quicker, more convenient, and more accessible due to the latest technologies. However, this has also raised brows on the level of security, especially for business communication. Today, organizations are concerned about protecting their valuable information. On the other hand, criminals also utilize the same technology to harm individuals and businesses. Technologies like VoIP and cloud communication have become crucial components of business and criminal activities.

As per the VoIP Fraud Analysis report, Simwood, 2015, a leading VoIP solutions provider had undertaken toll and dial-through frauds costing its consumer more than 46 billion USD. The fraudsters executed this cyber-criminal activity to scam people through this VOIP technology. All the phone calls made were via the internet. The caller posed as a legitimate business and requested personal and financial details from the receiver. The cases of such criminal activities leveraging VoIP technology have become frequent worldwide.

The rising numbers of VoIP fraud lie at the core of VoIP technology features. VoIP enables internet telephony using a local VoIP number with no physical existence. Therefore, criminals can use a VoIP number with the minimal risk of being caught as it is hard to track the location of such numbers. As VoIP hardware has become readily available in the open market, criminals and scammers are using it and getting away with all the crimes. A scammer can quickly call up people using a VoIP number and pretend to be a bank representative or government employee. Most people give their critical information relying on the caller in such cases. The scammer uses the details to access the receiver’s credit card, debit card, or bank account to siphon off their money.

This scam may not seem new, as criminals have played the same trick for years through the old telephone system. The criminals were grabbed in such cases and always risked being traced. But today, with the help of a multi tenant IP PBX solution, criminals do not have a fear of being traced. These scammers easily fool people who aren’t tech-savvy and leverage official-sounding phone numbers to make calls to these people. They usually target aged or not-so-educated people to catch them off-guard and siphon their money by confusing them. It can be a call about a supposedly long-forgotten fixed deposit, a loan, or an inheritance of a distant relative. The scammers can come up with any pretense to trap people and get access to their critical information.

How to detect and counter illegal VoIP?

When VoIP calls are transmitted through illegal routes, they are transmitted through a mobile network to bypass the designated International Gateway. For instance, when we make calls through Skype or Yahoo Messenger, those calls don’t need a SIM card for execution. In short, there are Softswitch servers that relay these calls through the internet. Asterisk is an example of a server where most countries have implemented multiple regulations and laws to get VoIP systems. Law enforcement bodies monitor and analyze network traffic to prevent illegal VoIP.

The voice signals are encrypted through the server as data packets while making a VoIP call. Before the VoIP call is transmitted to the receiver, it has to bypass a pre-programmed computer. It checks the credit available to the VoIP number and if it has enough credit, the call is transmitted to the available SIM in the other country. The call is finally transferred to the called number from a local number through telecom infrastructure through this SIM. Caller ID software such as MagicDial can be used to mask the number for further protection. Therefore, Caller ID analysis cannot serve as a full-proof method to detect illegal VoIP.

The only way to limit illegal VoIP or grey traffic is to develop techniques to detect such calls. It requires analysis of IP traffic to detect, block or charge such illegal VoIP calls. One of the ways to execute this plan is by inspecting call detail records (CDRs). It records all the details of calls made through PSTN and IP telephony. The call logs in CDR disclose the source and destination of every call along with duration, date, and time. Call logs are used not just for illegal communication detection but also for several financial, billing, and engineering purposes. Therefore, monitoring and detecting illegal VoIP through this technique have become complex and expensive. Moreover, this method only infers whether the calls are white or grey. Therefore, it is not accurate in terms of illegal VoIP detection.

An alternative to this technique is the detection of illegal VoIP using pcap files. CDRs extract call logs based on required parameters by analyzing and filtering these files. Once done, the CDRs detect whether the call is legal or illegal through grey-and-white signaling. While doing so, the VoIP call is captured in the form of data packets and stored in a Pcap file. This capturing of VoIP packets is done through the Wireshark tool.

Unfortunately, VoIP at the application layer has no developed techniques to detect illegal calls. There are no standard algorithms for the same. However, an algorithm has been proposed to identify and detect illicit traffic VoIP. In this algorithm, the main focus lies on SIP to see illegal VoIP protocols. SIP is a protocol in text form, just like HTTP. It is the signaling that modifies and transmits different communication sessions. The algorithm proposed uses SIP in a similar format to HTTP to detect illegal VoIP activities. In this pcap programming, the algorithm filters SIP packets to extract call parameters from call logs or CDRs. It helps classify the calls generated by analyzing the call logs as legal or illegal VoIP traffic. Moreover, if engineers further build on this pcap programming to develop an algorithm that can be implemented for offline real-time data analysis. It will also eliminate the need for using tools like Wireshark.

VoIP developers are still working on developing a cost-efficient technique to prevent illegal VoIP activities. It is imperative to develop and implement a practical algorithm that can be standardized to detect unlawful VoIP.

The Bottom Line

The issue of Illegal VOIP is a global issue since it is most common in developing countries. But, it is also an issue in developed countries. The way it is dealt with within developed countries is different from in developing countries. Many developing countries do not have the resources or laws to deal with it. There are a few ways to deal with it; the first step is detecting illegal VOIP, which is essential. There are many ways to do this through data analysis and summarization. With the help of this, illegal VoIP data can be detected.

To know more about illegal VoIP or VoIP frauds connect with our team at +91-7778842856 (INDIA) / +1-303-997-3139 (USA) or write to

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