Data Interception and Theft

When packets travel across a network, they are susceptible to being read, altered, or “hijacked.” Hijacking occurs when a hostile party intercepts a network traffic session and poses as one of the session endpoints.

An attacker monitors data streams to or from a target, in order to gather sensitive information. This attack usually involves sniffing network traffic, but may include observing other types of data streams. Sniffing or eavesdropping is the act of monitoring traffic on the network for data such as plaintext passwords or configuration information. With a simple packet sniffer, an attacker can easily read all plaintext traffic.

In most varieties of this attack, the attacker is passive and simply observes regular communication, however in some variants the attacker may attempt to initiate the establishment of a data stream or influence the nature of the data transmitted. In all variants of this attack, and distinguishing it from other data collection methods, the attacker is not the intended recipient of the data stream. Unlike some other data leakage attacks, the attacker is observing explicit data channels (e.g. network traffic) and reading the content. This differs from attacks that collect more qualitative information, such as communication volume, or other information not explicitly communicated via a data stream.

The tool that is used for data interception is called packet analyzer or packet sniffer. This is a computer program or a piece of computer hardware that can intercept and log traffic passing over a digital network or part of a network. As data streams flow across the network, the sniffer captures each packet and, if needed, decodes the packet’s raw data, showing the values of various fields in the packet, and analyzes its content according to the appropriate RFC or other specifications.

Data interception can be used by law enforcement agencies, regulatory or administrative agencies, and intelligence services, in accordance with local law. This is known as Lawful Interception and it is meant for the purpose of analysis of traffic. There are many bases for this activity that include infrastructure protection and cyber security. In general, the operator of public network infrastructure can undertake Lawful Interception activities for those purposes. Operators of private network infrastructures have an inherent right to maintain Lawful Interception capabilities within their own networks unless otherwise prohibited.


To protect your data from the interception you should use strong traffic encryption.

Virtual private networks (VPNs) allow secure access to corporate resources by establishing an encrypted tunnel across the Internet. The ubiquity of the Internet, combined with the VPN technologies of today, allows organizations to cost-effectively and securely extend the reach of their networks to anyone, anyplace, anytime.


IPSec is a framework of open standards developed by the Internet Engineering Task Force (IETF) that provides security for transmission of sensitive information over unprotected networks such as the Internet. IPSec acts at the network layer, protecting and authenticating IP packets between participating IPSec devices (“peers”).

IPsec is designed to provide interoperable, high-quality, and cryptographically based security. IPsec is defined in (RFC 2401). The set of security services offered includes access control, connectionless integrity, data origin authentication, protection against replays, confidentiality (encryption), and limited traffic flow confidentiality. These services are provided at the IP layer, offering protection for IP and upper-layer protocols (ULPs). Because these services are provided at the IP layer, they can be used by any higher-layer protocol (for example TCP, User Datagram Protocol [UDP], and Border Gateway Protocol [BGP]).

IPsec provides security services at the IP layer by enabling a system to select required security protocols, determine the algorithm (or algorithms) to use for the service (or services), and put in place any cryptographic keys required to provide the requested services. IPsec can be used to protect one or more paths between a pair of hosts, between a pair of security gateways, or between a security gateway and a host.

IPSec provides the following network security services.

• Data Confidentiality—The IPSec sender can encrypt packets before transmitting them across a network.

• Data Integrity—The IPSec receiver can authenticate packets sent by the IPSec sender to ensure that the data has not been altered during transmission.

• Data Origin Authentication—The IPSec receiver can authenticate the source of the IPSec packets sent. This service is dependent upon the data integrity service.

• Anti-Replay—The IPSec receiver can detect and reject replayed packets.

IPSec prevents routed traffic from being examined or tampered with while it travels across a network. This feature causes IP packets to be encrypted at a VPN gateway, routed across a network as encrypted information, and decrypted at the destination VPN gateway. In between the two VPN gateways, the packets are in encrypted form and therefore the packets’ contents cannot be read or altered. You define what traffic should be encrypted between the two VPN gateways, according to what data is more sensitive or critical.

If you want to protect traffic for protocols other than IP, you can encapsulate those other protocols into IP packets using GRE encapsulation, and then encrypt the IP packets.


802.1AE is the IEEE MAC Security standard (also known as MACsec) which defines connectionless data confidentiality and integrity for media access independent protocols.

MACsec allows unauthorized LAN connections to be identified and excluded from communication within the network. In common with IPsec and SSL, MACsec defines a security infrastructure to provide data confidentiality, data integrity and data origin authentication.

MACsec is the IEEE 802.1AE standard for authenticating and encrypting packets between two MACsec-capable devices. Cisco switches like Catalyst 4500 series support 802.1AE encryption with MACsec Key Agreement (MKA) on downlink ports for encryption between the switch and host devices. The switches also supports MACsec link layer switch-to-switch security by using Cisco TrustSec Network Device Admission Control (NDAC) and the Security Association Protocol (SAP) key exchange. Link layer security can include both packet authentication between switches and MACsec encryption between switches (encryption is optional).

MACsec, defined in 802.1AE, provides MAC-layer encryption over wired networks by using out-of-band methods for encryption keying. The MACsec Key Agreement (MKA) Protocol provides the required session keys and manages the required encryption keys. MKA and MACsec are implemented after successful authentication using the 802.1X Extensible Authentication Protocol (EAP) framework. Only host facing links (links between network access devices and endpoint devices such as a PC or IP phone) can be secured using MACsec.

A switch using MACsec accepts either MACsec or non-MACsec frames, depending on the policy associated with the client. MACsec frames are encrypted and protected with an integrity check value (ICV). When the switch receives frames from the client, it decrypts them and calculates the correct ICV by using session keys provided by MKA. The switch compares that ICV to the ICV within the frame. If they are not identical, the frame is dropped. The switch also encrypts and adds an ICV to any frames sent over the secured port (the access point used to provide the secure MAC service to a client) using the current session key.

The EAP framework implements MKA as a newly defined EAP-over-LAN (EAPOL) packet. EAP authentication produces a master session key (MSK) shared by both partners in the data exchange. Entering the EAP session ID generates a secure connectivity association key name (CKN). Because the switch is the authenticator, it is also the key server, generating a random 128-bit secure association key (SAK), which it sends it to the client partner. The client is never a key server and can only interact with a single MKA entity, the key server. After key derivation and generation, the switch sends periodic transports to the partner at a default interval of 2 seconds.


The SSL VPN feature (also known as WebVPN) provides support, in Cisco IOS software, for remote user access to enterprise networks from anywhere on the Internet. Remote access is provided through a Secure Socket Layer- (SSL-) enabled SSL VPN gateway. The SSL VPN gateway allows remote users to establish a secure Virtual Private Network (VPN) tunnel using a web browser. This feature provides a comprehensive solution that allows easy access to a broad range of web resources and web-enabled applications using native HTTP over SSL (HTTPS) browser support.

WebVPN lets users establish a secure, remote-access VPN tunnel to a security appliance using a web browser. Users do not need a software or hardware client. WebVPN provides secure and easy access to a broad range of web resources and web-enabled applications from almost any computer on the Internet. WebVPN uses Secure Sockets Layer Protocol and its successor, Transport Layer Security to provide the secure connection between remote users and specific, supported internal resources that you configure at a central site. The security appliance recognizes connections that need to be proxied, and the HTTP server interacts with the authentication subsystem to authenticate users.