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In this paper, we perform an empirical analysis of the cyber criminal ecosystem on Twitter. Essentially, through analyzing inner social relationships in the criminal account community, we find that criminal accounts tend to be socially connected, forming a small-world network. We also find that criminal hubs, sitting in the center of the social graph, are(More)
We systematically study the design of image recognition CAPTCHAs (IRCs) in this paper. We first review and examine all existing IRCs schemes and evaluate each scheme against the practical requirements in CAPTCHA applications, particularly in large-scale real-life applications such as Gmail and Hotmail. Then we present a security analysis of the(More)
We will discuss the recurrence on the state space of the adaptive MCMC algorithm using some examples. We present the ergodicity properties of adaptive MCMC algorithms under the minimal recurrent assumptions, and show the Weak Law of Large Numbers under the same conditions. We will analyze the relationship between the recurrence on the product space of state(More)
To date, as one of the most popular Online Social Networks (OSNs), Twit-ter is paying its dues as more and more spammers set their sights on this microblogging site. The Twitter spammers can achieve their malicious goals such as sending spam, spreading malware, hosting botnet command and control (C&C) channels, and launching other underground illicit(More)
BACKGROUND In mass spectrometry (MS) based proteomic data analysis, peak detection is an essential step for subsequent analysis. Recently, there has been significant progress in the development of various peak detection algorithms. However, neither a comprehensive survey nor an experimental comparison of these algorithms is yet available. The main objective(More)
In this paper, we consider the problem of “evil twin” attacks in wireless local area networks (WLANs). An evil twin is essentially a rogue (phishing) Wi-Fi access point (AP) that looks like a legitimate one (with the same SSID). It is set up by an adversary, who can eavesdrop on wireless communications of users' Internet access. Existing evil(More)
Starting with the seminal paper of Haario, Saksman and Tamminen (Haario et al. (2001)), a substantial amount of work has been done to validate adaptive Markov chain Monte Carlo algorithms. In this paper we focus on two practical aspects of adaptive Metropolis samplers. First, we draw attention to the deficient performance of standard adaptation when the(More)
Strigolactones (SLs), a newly discovered class of carotenoid-derived phytohormones, are essential for developmental processes that shape plant architecture and interactions with parasitic weeds and symbiotic arbuscular mycorrhizal fungi. Despite the rapid progress in elucidating the SL biosynthetic pathway, the perception and signalling mechanisms of SL(More)
An efficient parallel algorithm is presented and tested for computing selected components of H −1 where H has the structure of a Hamiltonian matrix of two-dimensional lattice models with local interaction. Calculations of this type are useful for several applications, including electronic structure analysis of materials in which the diagonal elements of the(More)