It is crucial for public users and service providers to stay abreast of the progress and trends on data exfiltration in computer security system. In cryptosystem, it is unnoticeable for computer and mobile users to realize that inaudible sound used to transmit signals carrying pervasive sensitive data was in the low frequency ultrasonic range. Acoustic attacks on ultrasonic signal emanated by electronic devices have long been investigated among researchers. This paper is an exploration on the practicality of ultrasonic data exfiltration between computers in term of computer security system. It will discuss some work done by previous researchers in general, based on scientific, technological, and security perspectives. There will be inclusions of practical applications already in existence as well as future studies in related fields.

The ionospheric F-layer profiles over Parit Raja (Lat. 1�52'N, Long. 103�48'E, Magnetic dip 14.3�) are observed for 5 days; from January 14 to January 18, 2005, a period in moderate solar epoch. Analyses show that the ionospheric profiles development and decay are accompanied by the rise and fall in the height associated to the profile density. The profile peak reaches its highest level during noon and lowest during pre-sunrise, under normal condition. Mixed profiles are observed during disturbed condition. The density size expands but reduction in peak height is observed. In addition, the electron density profile can also be a pre-cursor to the occurrence of spread-F. � 2014 IEEE.

This paper investigates the capabilities of Neural Network (NN) application in estimating the missing ionospheric total electron content (TEC) data via interpolation and extrapolation methods. TEC is an important parameter that describes the state of the ionosphere. A multilayer feed-forward network with a back propagation algorithm is applied to estimate the TEC over Parit Raja (Lat. 1�52?N, Long. 103�06?E) an equatorial latitude station in Malaysia. The solar and magnetic indices, seasonal variation as well as diurnal variation are used as the input spaces in the NN to estimate the missing GPS TEC. The studies period is based on short term data during the medium solar activity period from 2005 to 2006. Normalized RMSE, RMSE and relative correction are computed for both methods to evaluate the capability of NN to interpolate and extrapolate the missing data. The results show that NN is able to interpolate the missing TEC data within the input range better than extrapolating the missing data outside the input range. The NN2 model finds hard to extrapolate the missing TEC data especially during the night hours, where the GPS TEC values are underestimated. Overall the relative correction of NN1 model is above 90% while for NN2 is below 90% for all ranges of missing rate. � 2016 IEEE.

This paper introduces a new alternative in representing temporal ionospheric height of peak electron density, hmax, variations using array antenna parameters. The use of polar cyclic diagram based on antenna radiation pattern is proposed. The height variations are illustrated using arrays of two-element arrays with array spacing in the x-direction of ? /8, and phase of ? /3, and with element spacing in the y-direction of ? /4, and phase of zero. The antenna equivalent model of peak height variations may complement the classical way of representing hmaxtemporal variations and acts as a signature to any ionospheric height of peak density variations. It constitutes the novelty of the study. � 2014 IEEE.