How where is captcha being utilized

A wide variety of devices qualifies to be used by this authentication method. The minimum requirements are: the storage of data such as a private key, the ability to communicate, and a processor to perform the cryptographic operations. Smart devices possess these requirements and the manufacture of such devices can be realized at a reasonable cost.

This method is malleable and implemented in numerous authentication protocols. This thesis illustrates and explains several instances of these protocols. The method's primary novelty is its resistance to theft-based attacks, which results from the utilization of multiple devices to authenticate users.

A user associated with multiple devices needs to be in possession of these devices to correctly perform the authentication task. This thesis focuses on the system design of this novel authentication method.

Abstract: Since authentication is the key to access control security in Internet access for every user, therefore, how to verify a user is who he claimed to be is a very important requirement in Internet security. In some situations, users need to be re-authenticated to make sure that they are still actively engaged in real time interaction. For instance, people will be notified to dial to a specific server phone number to reconfirm his identity again before re-login using their account ID and passwords pairs.

This approach has been adopted by many online game servers. If the reading fails, the design is robust. The main effects of all three variables and few of the interaction effects on robustness were significant. The findings have both theoretical and practical contributions. It requires the deciphering of distorted texts, mostly in English that computers still cannot do well. It is also helpful in preventing the abuse of online services.

Abstract: Online services which allow users to contribute content and interact remotely over the internet in some manner are common today. Many of these services, like spam control for blogs and email account sign-up, require that they be accessed only by humans and not machines automated scripts or bots.

We explore three primary tracks of investigation in this work. We present techniques for simulating handwriting without being writer-specific. Unlike previous work, this is a fully-automated approach based on extracting principal curves from handwritten characters. These serve as a set of control points to allow character-level distortion. We use novel techniques for character baseline detection and ligature parameterization to construct the textlines.

A parameterized sinusoid-based function is used to allow random perturbation of these textlines. Abstract: Web crawlers have been developed for several malicious purposes like downloading server data without permission from website administrator. Armored stealthy crawlers are evolving against new anti-crawler mechanisms in the arms race between the crawler developers and crawler defenders.

In this paper, we develop a new anti-crawler mechanism called PathMarker to detect and constrain crawlers that crawl content of servers stealthy and persistently.

By using the URL path and user information contained in the marker as the novel features of machine learning, we could accurately detect stealthy crawlers at the earliest stage. Besides effectively detecting crawlers, PathMarker can also dramatically suppress the efficiency of crawlers before they are detected by misleading the crawlers visiting same page's URL with different markers.

We deploy our approach on a forum website to collect normal users' data. The evaluation results show that PathMarker can quickly capture all 12 open-source and in-house crawlers, plus two external crawlers i. Most existing schemes defend attacks by increasing deformation or distortion rate of words which sacrifice the friendliness of the system.

The core of our design is an information obfuscation scheme which determines which character image to display and which to hide in an online manner from a sequence of 62 character images which makes it more difficult to attack.

Encryption method is employed for protecting display policies which control showing and hiding of information. Prototype has been implemented and the preliminary results are encouraging. Abstract: This dissertation presents a series of techniques that help both client devices and network elements defend against a wide variety of worm attacks.

These techniques can be deployed to secure emergent networks including peer-to-peer P2P file-sharing systems and wireless communication systems. In recent years, worms have emerged as one of the most disastrous security threats to various information systems and network infrastructures.

Although Internet worms have been extensively studied, worm issues in such emergent networks as peer-to-peer P2P systems and cellular networks have yet received due attention. This dissertation aims at designing automated, realtime, and systematic countermeasures, which leverage the existing internal communication mechanisms and network infrastructure to contain worm propagation.

The proposed defenses consist of security solutions for both client and system software. For P2P networks, this dissertation first proposes a partition-based scheme and a CDS-based scheme to contain ultra-fast topological worm spreads.

These schemes leverage the underlying P2P overlay for distributing automated security patches to vulnerable machines. They are unique in adopting graph-theory techniques for containing fast spreading worms. This dissertation then proposes a P2P-tailored solution to combat file-sharing worms in P2P environments. Our solution consists of a download-based scheme and a search-based scheme.

Both schemes utilize the existing file-sharing mechanisms to internally disseminate security patches to participating peers in a timely and distributed fashion. For cell-phone networks, this dissertation proposes two device-level defenses for securing smartphone software, namely an access-control—based scheme and a GTT-based scheme. These schemes are unique in that they either enforce security policies in phone devices to identify and block worm attacks or leverage artificial intelligence AI methods to differentiate human or worm initiators of the phone applications.

This dissertation also proposes a systematic countermeasure consisting of both terminal-level and network-level defenses for combating cell-phone worms. Unlike the existing solutions that split the collaboration between the terminal device and the network to throttle system-wide worm spreads, the proposed solution adopts an identity-based signature scheme at both the sender and the receiver side, and a detection-based automated patching scheme at the network side.

Combining terminal-level and network-level defenses effectively speeds up the process of worm detection and victim disinfection. This dissertation also provides solid mathematical analyses, extensive simulations and experiments to evaluate the effectiveness and show the applicability of the proposed defenses.

In addition, it discusses some open issues related to the proposed solutions and suggests some interesting directions in combating the worm threats as the emergent networks evolve. Abstract: The continuous stream of videos that are uploaded and shared on the Internet has been leveraged by computer vision researchers for a myriad of detection and retrieval tasks, including gesture detection, copy detection, face authentication, etc. However, the existing state-of-the-art event detection and retrieval techniques fail to deal with several real-world challenges e.

More importantly, my work highlights the fact that the choice of underlying hard problem selected by the designers of a leading commercial solution falls into a solvable subclass of computer vision problems. For face liveness detection, I introduce a novel approach to bypass modern face authentication systems. More specifically, by leveraging a handful of pictures of the target user taken from social media, I show how to create realistic, textured, 3D facial models that undermine the security of widely used face authentication solutions.

My framework makes use of virtual reality VR systems, incorporating along the way the ability to perform animations e. I demonstrate that such VR-based spoofing attacks constitute a fundamentally new class of attacks that point to a serious weaknesses in camera-based authentication systems.

For reconstructing typed input on mobile devices, I proposed a method that successfully transcribes the text typed on a keyboard by exploiting video of the user typing, even from significant distances and from repeated reflections.

To assess the viability of a video confirmation attack, I explored a technique that exploits the emanations of changes in light to reveal the programs being watched. I leverage the key insight that the observable emanations of a display e.

Lastly, for content-based copy detection, I take advantage of a new temporal feature to index a reference library in a manner that is robust to the popular spatial and temporal transformations in pirated videos. My technique narrows the detection gap in the important area of temporal transformations applied by would-be pirates.

My large-scale evaluation on real-world data shows that I can successfully detect infringing content from movies and sports clips with In contrast to early work that relied on sophisticated computer vision or machine learning techniques, the authors used simple pattern recognition algorithms to exploit fatal design errors.

On the other hand, most of the traditional CPATCHAs require complicated operations using keyboards and mice which may become limitations of modern handset devices. The formula is able to improve the problems of rampant Internet fishing and the management of passwords. In techniques, on one hand, it uses PIN information visual passwords in cell phones to improve the security of the account on the other hand, it uses voiceprint identification features so that the system center can ensure the user's identification with a view to improve the leak in mobile devices rather than only to check mobile devices.

Through the frame of this research, it can protect our cell phones from being lost and embezzled and can prevent the account and passwords from being attacked by Internet fishing. It can also solve the problem of users forgetting accounts and passwords, and reduce the operational burden of cell phones. Besides, it is capable of preventing the Cloud servers from incurring many malicious registrations and logins, keeping them working efficiently.

Abstract: Spam messages are an increasing threat to mobile communication. Several mitigation techniques have been proposed, including white and black listing, challenge-response and content-based filtering.

However, none are perfect and it makes sense to use a combination rather than just one. We propose an anti-spam framework based on the hybrid of content-based filtering and challenge-response. A message, that has been classified as uncertain through content-based filtering, is checked further by sending a challenge to the message sender.

An automated spam generator is unlikely to send back a correct response, in which case, the message is classified as spam. Our simulation results show the trade-off between the accuracy of anti-spam classifiers and the incurring traffic overhead, and demonstrate that our hybrid framework is capable of achieving high accuracy regardless of the content-based filtering algorithm being used.

Moradi, M. From Research Questions Task Force. Jump to: navigation , search. Navigation menu Personal tools Log in. Namespaces Page Discussion. Views Read View source View history. You, yes you, dear reader, have been part of something incredible.

Thanks to your hard work, millions of books containing pretty much the sum-total of human knowledge have been successfully digitised, saving their texts for future generations.

All because of you. The premise was as described above: by marrying up users who need to prove they are human to data that needs transcribing, both sides get something out of it. So instead of digitising books by having one person carry out the very boring task of typing or checking a whole book manually, instead millions of people can unknowingly collaborate to achieve the same goal. Remember how it always used to be two words you had to enter? Subscribe to our channel to stay updated.

Our mission has never been more vital than it is in this moment: to empower through understanding. Financial contributions from our readers are a critical part of supporting our resource-intensive work and help us keep our journalism free for all.

Please consider making a contribution to Vox today to help us keep our work free for all. Cookie banner We use cookies and other tracking technologies to improve your browsing experience on our site, show personalized content and targeted ads, analyze site traffic, and understand where our audiences come from. By choosing I Accept , you consent to our use of cookies and other tracking technologies. Reddit Pocket Flipboard Email. Next Up In Video.