Clicktok : click fraud detection using traffic analysis

Advertising is a primary means for revenue generation for millions of websites and smartphone apps. Naturally, a fraction abuse ad networks to systematically defraud advertisers of their money. Modern defences have matured to overcome some forms of click fraud but measurement studies have reported that a third of clicks supplied by ad networks could be clickspam. Our work develops novel inference techniques which can isolate click fraud attacks using their fundamental properties.We propose two defences, mimicry and bait-click, which provide clickspam detection with substantially improved results over current approaches. Mimicry leverages the observation that organic clickfraud involves the reuse of legitimate click traffic, and thus isolates clickspam by detecting patterns of click reuse within ad network clickstreams. The bait-click defence leverages the vantage point of an ad network to inject a pattern of bait clicks into a user's device. Any organic clickspam generated involving the bait clicks will be subsequently recognisable by the ad network. Our experiments show that the mimicry defence detects around 81% of fake clicks in stealthy (low rate) attacks, with a false-positive rate of 110 per hundred thousand clicks. Similarly, the bait-click defence enables further improvements in detection, with rates of 95% and a reduction in false-positive rates of between 0 and 30 clicks per million - a substantial improvement over current approaches

Studies on L-cystine hydrobromide single crystals for nonlinear optical applications

l-cystine hydrobromide (LCHBr) is a novel nonlinear optical material which has been synthesized and grown. The low-temperature solution growth technique was employed to grow the single crystal of LCHBr. The structure of the grown crystals was characterized by single-crystal XRD. The different functional groups of the grown LCHBr crystal are studied using FTIR spectroscopy. The transparent nature of the grown crystal was analysed by UV–Vis–NIR study. The mechanical strength of the grown crystal was analysed using microhardness study. The optical second harmonic generation conversion efficiency of the LCHBr crystal was studied using Nd:YAG laser. The laser damage threshold value of this grown crystal has been evaluated

Synthesis, growth and characterization of a nonlinear optical crystal: l-Leucinium perchlorate

An amino acid based semiorganic nonlinear optical family single crystal of l-leucinium perchlorate (LLPCl) was grown by the solvent evaporation method at ambient temperature. Good optical quality single crystals up to a size of 6 mm × 5 mm × 3 mm were obtained. The single-crystal XRD analysis shows that the grown crystals have a monoclinic structure. Fourier transform infrared (FTIR) spectral analysis and UV–vis spectral studies were also carried out. Microhardness mechanical studies show that the hardness number (Hv) of a LLPCl single crystal decreases with the load as measured by the Vickers microhardness method. The dielectric properties of the grown crystal were analysed by varying the frequency. Photoconductivity analysis gives the variation of the photocurrent and dark current. The nonlinear optical properties were studied using the Kurtz and Perry powder method and the second harmonic generation efficiency was found to be 2.6 times higher than that of KDP crystals