Cyber Defense eMagazine July Edition for 2022

M2M communication security is required to safeguard the system from all forms of threats and infiltration.
This includes means to prevent denial-of-service (DoS) attacks, transmission eavesdropping, routing
attacks, floods, and data center security and access control. Physical attacks include inserting legitimate
authentication tokens into a manipulated device, modifying or changing software, and
environmental/side-channel attacks. A DoS attack is one that attempts to bring a system or network to a
halt, rendering it unreachable to its intended users. SDRs are capable of protecting against these since
they are networked devices and can be used as a barrier by monitoring data being received/transmitted
at the SDR gateway (via FPGA end-point security, etc.) before being passed over to other network
components (cloud servers in data centers, other IIoT devices, etc.), as well as alert of any suspicious
activities.
One important aspect to consider is the use of SDR in the IIoT communication stack such as to self-heal,
autoconfigure, and adapt the radio based on various EMS environments. For instance, there is always a
chance that data communications could be harmed by radio frequency (RF) interference, which is
unwanted energy in the form of emissions, radiations, or inductions. RF interference can affect a wide
range of wireless technologies, including Bluetooth, Wi-Fi, and GPS. On the other hand, jamming occurs
between a transmitter and a receiver. The purpose of radiofrequency or communication jamming is to
prevent receiving or decoding, by disabling the opponent's radio connection. To respond to these
incidents, SDRs can reconfigure by various means, such as changing antenna directionality, changing
center frequency, or using a redundant SDR gateway elsewhere in an IIoT network, thus mitigating RF
spectral issues.
Other schemes for a secure SDR architecture incorporate an automatic calibration and certification unit
(ACU), an radio security module (RSM), and a GNSS receiver for the position. The ACU is an SDR
security threat mitigation method that monitors the output spectrum to enforce local rules. Such systems
may set the necessary spectrum rules depending on the SDR's location and spectrum configuration files.
The SDR monitors spectrum laws globally (for example, spectrum configuration files). Even a malicious
waveform in the SDR node can be stopped by the ACU. These modules are downloaded and executed
by the RSM. User and device authentication, event and access logging, encryption, port disabling, and
smart password and network key management are also important to consider.
Current research is also being done on SDRs used to prevent issues related to co-channel interference.
As mentioned, one common IIoT protocol is Zigbee, however, it suffers from co-channel interference with
WiFi sharing the same band. At 2.4 GHz, ZigBee uses offset quadrature phase-shift keying (O-QPSK)
and direct-sequence spread spectrum (DSSS). But, each WiFi orthogonal channel has four ZigBee
channels (2 MHz each), and thus, buried or blind terminals, and variations in channel sensing/response
time still cause co-channel interference. To prevent this, matching local noise variance (LNV) is estimated
after the interferers appear, and the Log-likelihood ratios (LLRs) are scaled using Local noise variance
LLR scaling (LNV-SC). Figure 2 depicts the full interference detection and LLR scaling process. Adding
LLRs to SDR software simplifies implementation. In an article published in IEEE Transactions on
Vehicular Technology, researchers from Oulu University in Finland and Kaiserslautern University in
Germany demonstrated how SDR can successfully mitigate the effects of multiple co-channel ZigBee
interferers. The researchers found that SDR-based interference reduction may considerably improve
ZigBee network performance in both lab and field settings.
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