Demystifying Telecom Security: A Practical Guide to SS7 Testing with SigPloit

he world of cybersecurity is often hyper-focused on web applications, cloud infrastructure, and internal corporate networks. But beneath all of that lies the invisible backbone of global communication: telecom networks. Every time you make a call, send an SMS, or roam in a foreign country, massive core network switches are quietly talking to each other.

And for a long time, those conversations have been implicitly trusted.

If you are a penetration tester looking to expand your vulnerability assessment and penetration testing (VAPT) repertoire, telecom signaling security is a fascinating, high-stakes domain. Here is a breakdown of what telecom testing is, how the legacy SS7 protocol works, and a practical guide to setting up and running your first assessment using the SigPloit framework.

What is Telecom Testing?

Telecom security testing (or signaling security assessment) is the process of evaluating the core network infrastructure of a Mobile Network Operator (MNO) or a Mobile Virtual Network Operator (MVNO).

Instead of attacking web servers, you are analyzing the interfaces that handle subscriber authentication, call routing, and data sessions. The goal is to determine if an external attacker — or a compromised international roaming partner — can exploit these networks to track a user's location, intercept SMS messages (like 2FA codes), intercept calls, or perform billing fraud.

Testing usually spans several protocol generations, including SS7 (2G/3G), Diameter (4G/LTE), and GTP (data plane tunneling).

What is SS7?

Signaling System №7 (SS7) is a set of telephony signaling protocols developed in the 1970s. It is the language that telecom networks use to communicate with one another across the globe.

The fundamental flaw of SS7 is that it was built on a "walled garden" trust model. When the protocol was designed, only a handful of state-owned monopolies had access to the network. Therefore, the protocol assumes that if a message comes from within the SS7 network, it must be legitimate. There is no built-in encryption or strict authentication for routing messages.

Today, access to the SS7 network can be purchased or leased by thousands of third-party aggregators and virtual operators. If a malicious actor gains access to an SS7 entry point, they can send unauthorized MAP (Mobile Application Part) queries to a target network's Home Location Register (HLR) — the master database of subscribers.

Without strict signaling firewalls in place, an attacker can use queries like SendRoutingInfoForSM to extract a subscriber's IMSI (International Mobile Subscriber Identity) and their current physical location (down to the serving switch).

Prerequisites for Telecom Testing

You cannot simply fire up a scanner against a random IP address to test telecom protocols. Signaling networks are tightly controlled. Before you begin, you need a solid testing foundation:

• Authorized Rules of Engagement (RoE): You must have explicit, documented permission, including the specific target gateways, test subscriber MSISDNs (phone numbers), and the authorized Global Titles (GTs) you are allowed to spoof.
• Network Access: Telecom nodes do not typically sit on the public internet. You will either need your public IP whitelisted through the client's IT perimeter firewall, a dedicated VPN to their testbed, or a provisioned test SIM card tethered to your machine to test directly from the User Plane.
• M3UA Routing Configuration: Telecom switches use Point Codes (OPC/DPC) to route traffic at the M3UA transport layer. For an external test to successfully reach the core network, the client's engineers must often build a temporary M3UA Application Server link mapping your Originating Point Code to their destination. If this isn't configured, your traffic will be dropped at the routing layer before the exploit ever fires.
• The Right OS: A Linux distribution, preferably Kali Linux, equipped with network analysis tools like Wireshark.

How to Install SigPloit in Kali Linux

SigPloit is a comprehensive signaling exploitation framework. However, because it is a legacy tool originally built on Python 2.7, installing it on modern Linux distributions requires some manual dependency management. Python 2 reached its end of life in 2020, and modern build environments frequently break when trying to compile legacy networking libraries like pysctp.

Here is the bulletproof way to install SigPloit on a modern Kali system:

1. Install System Dependencies Before Python can build the SCTP wrappers, your OS needs the C-compilers and SCTP development headers, as well as legacy cryptography libraries.

sudo apt update
sudo apt install python2 python2-dev libsctp-dev build-essential libcrypt-dev

sudo apt update
sudo apt install python2 python2-dev libsctp-dev build-essential libcrypt-dev

2. Bootstrap the Legacy pip2 Installer Modern repositories no longer host pip2, so you must download the official PyPA bootstrap script:

curl https://bootstrap.pypa.io/pip/2.7/get-pip.py -o get-pip.py
sudo python2 get-pip.py

curl https://bootstrap.pypa.io/pip/2.7/get-pip.py -o get-pip.py
sudo python2 get-pip.py

3. Upgrade Setuptools To prevent error: invalid command 'egg_info' when building packages from source, upgrade your build tools:

sudo python2 -m pip install --upgrade setuptools wheel

sudo python2 -m pip install --upgrade setuptools wheel

4. Clone and Install SigPloit Clone the repository and install the requirements. Crucially, append the --no-use-pep517 flag. This forces pip to bypass modern, isolated build environments that fail on legacy Python 2 C-extensions (specifically pysctp).

git clone https://github.com/SigPloiter/SigPloit.git
cd SigPloit
sudo pip2 install -r requirements.txt --no-use-pep517

git clone https://github.com/SigPloiter/SigPloit.git
cd SigPloit
sudo pip2 install -r requirements.txt --no-use-pep517

How to Use SigPloit

Once installed, launch the framework using sudo python2 sigploit.py. The interface is menu-driven and intuitive.

1. Configure Connection Parameters Before launching an attack, you must define the transport pathway.

• client_ip & server_ip: Your testing IP and the target gateway IP.
• client_pc & server_pc: Your Originating Point Code (OPC) and Destination Point Code (DPC).
• routing_context: Provided by the network operator to map your specific session.

2. Configure Exploit Parameters For an SS7 tracking test, you will navigate to the SS7 menu, select Interception/Tracking, and configure the target details:

• target_msisdn: The phone number of the test subscriber.
• local_gt: The authorized Global Title you are spoofing to look like a legitimate SMSC or roaming partner.

3. Execute and Analyze Fire the test case (e.g., SendRoutingInfoForSM).

Simultaneously, run Wireshark in the background capturing on the SCTP protocol (port 2905).

Interpreting the Results: If the tool fails to return an IMSI, that is not a failure of the test — it is often a security finding. * If you see an M3UA error in Wireshark stating No AS found for routing message, it means the network's signaling firewall successfully blocked your unauthorized Point Code at the perimeter.

• If the message passes the M3UA layer but the HLR returns an Error: Facility Not Supported, it means the core network properly filters unauthorized Category 1/2/3 MAP messages.
• If the tool returns the IMSI and the VMSC (Visitor Mobile Switching Center) address, the network is vulnerable to location tracking and interception.

Telecom testing requires patience and a deep understanding of network architecture, but identifying and patching these core vulnerabilities is critical to securing global communications.