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SS7

The SS7 (Signaling System 7) protocol is a set of telephony signaling protocols that enable the communication and interaction between different nodes in the mobile network, such as switches, databases, and service control points. The SS7 protocol is used for various purposes, such as:

• Setting up, managing, and releasing voice calls and text messages.
• Performing number translation, local number portability, prepaid billing, and other services.
• Supporting roaming and interoperability among different mobile operators and regions.
• Enabling value-added services and features, such as call forwarding, call waiting, and call barring.

The SS7 protocol is based on the SS7 protocol family, which consists of four layers: MTP, SCCP, TCAP, and ISUP. Each layer provides different functions and services for the SS7 protocol, such as:

  1. MTP (Message Transfer Part): This layer is responsible for the reliable and efficient delivery of messages between the nodes in the SS7 network. It uses signaling links, signaling points, and signaling routes to establish and maintain the connections. It also performs error detection, correction, and congestion control.
  2. SCCP (Signaling Connection Control Part): This layer is responsible for the routing and addressing of messages between the nodes in the SS7 network. It uses global titles, point codes, and subsystem numbers to identify the nodes and the services they provide. It also supports connectionless and connection-oriented modes of communication.
  3. TCAP (Transaction Capabilities Application Part): This layer is responsible for providing the services of the SS7 network to the application layer, such as INAP, MAP, and CAP. It enables the exchange of messages and data between different nodes in the network, such as switches, databases, and service control points. It supports various functions, such as dialogue control, component handling, error detection, and security.
  4. ISUP (ISDN User Part): This layer is responsible for defining the messages and procedures for setting up, managing, and releasing voice calls over the SS7 network. It is used for both fixed and mobile telephony services, such as PSTN, ISDN, GSM, and UMTS.

OSI-SS7-SIGTRAN Protocol Stack

The SS7 protocol is widely used in mobile telephony, as it provides the necessary functions and features for the operation and management of the mobile network. However, the SS7 protocol also has some vulnerabilities and limitations, such as:

  • Lack of encryption and authentication: The SS7 protocol does not encrypt or authenticate the messages and data exchanged between the nodes, which makes it vulnerable to eavesdropping, spoofing, and manipulation by malicious actors.
  • Lack of security updates and patches: The SS7 protocol is an old and legacy protocol that has not been updated or patched to address the new and emerging threats and challenges in the mobile network.
  • Lack of trust and accountability: The SS7 protocol assumes that the nodes in the network are trustworthy and cooperative, which is not always the case in the current and complex mobile environment.

These vulnerabilities and limitations expose the mobile network and the users to various attacks and threats, such as:

  • Fraud: The attackers can use the SS7 protocol to perform unauthorized transactions, such as transferring money, buying goods, or subscribing to services, using the credentials and accounts of the legitimate users.
  • Interception: The attackers can use the SS7 protocol to intercept and access the voice calls and text messages of the users, as well as their personal and sensitive data, such as location, contacts, and passwords.
  • Tracking: The attackers can use the SS7 protocol to track and monitor the movements and activities of the users, as well as their habits and preferences, by obtaining their location data and call records.
  • DoS: The attackers can use the SS7 protocol to disrupt and degrade the performance and availability of the mobile network and the services, by flooding the nodes with fake or malicious messages and requests.

These attacks and threats pose serious risks and challenges for the mobile network and the users, as they compromise the security, privacy, and trust of the mobile communication. Therefore, there is a need for improving and enhancing the SS7 protocol, as well as developing and deploying new and alternative protocols, such as SIGTRAN, Diameter, and SIP, that can provide more secure and reliable mobile communication.

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