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Topic Review

Petya and NotPetya

Petya is a family of encrypting malware that was first discovered in 2016. The malware targets Microsoft Windows–based systems, infecting the master boot record to execute a payload that encrypts a hard drive's file system table and prevents Windows from booting. It subsequently demands that the user make a payment in Bitcoin in order to regain access to the system. Variants of Petya were first seen in March 2016, which propagated via infected e-mail attachments. In June 2017, a new variant of Petya was used for a global cyberattack, primarily targeting Ukraine . The new variant propagates via the EternalBlue exploit, which is generally believed to have been developed by the United States . National Security Agency (NSA), and was used earlier in the year by the WannaCry ransomware. Kaspersky Lab referred to this new version as NotPetya to distinguish it from the 2016 variants, due to these differences in operation. In addition, although it purports to be ransomware, this variant was modified so that it is unable to actually revert its own changes. The NotPetya attacks have been blamed on the Russian government, specifically the Sandworm hacking group within the GRU Russian military intelligence organization, by security researchers, Google, and several governments.

3.8K
19 Oct 2022

Topic Review

Location-Based Service

A location-based service (LBS) is a general term denoting software services which utilize geographic data and information to provide services or information to users. LBS can be used in a variety of contexts, such as health, indoor object search, entertainment, work, personal life, etc. Commonly used examples of location based services include navigation software, social networking services, location-based advertising, and tracking systems. LBS can also include mobile commerce when taking the form of coupons or advertising directed at customers based on their current location. They include personalized weather services and even location-based games. LBS is critical to many businesses as well as government organizations to drive real insight from data tied to a specific location where activities take place. The spatial patterns that location-related data and services can provide is one of its most powerful and useful aspects where location is a common denominator in all of these activities and can be leveraged to better understand patterns and relationships. Banking, surveillance, online commerce, and many weapon systems are dependent on LBS. Access policies are controlled by location data and/or time-of-day constraints, or a combination thereof. As such, an LBS is an information service and has a number of uses in social networking today as information, in entertainment or security, which is accessible with mobile devices through the mobile network and which uses information on the geographical position of the mobile device. This concept of location based systems is not compliant with the standardized concept of real-time locating systems (RTLS) and related local services, as noted in ISO/IEC 19762-5 and ISO/IEC 24730-1. While networked computing devices generally do very well to inform consumers of days old data, the computing devices themselves can also be tracked, even in real-time. LBS privacy issues arise in that context, and are documented below.

3.8K
25 Oct 2022

Topic Review

The 214 Kangxi radicals (Chinese: 康熙部首; pinyin: Kāngxī bùshǒu), also known as the Zihui radicals, form a system of radicals (部首) of Chinese characters. The radicals are numbered in stroke count order. They are the most popular system of radicals for dictionaries that order Traditional Chinese characters (hanzi, hanja, kanji, chữ hán) by radical and stroke count. They are officially part of the Unicode encoding system for CJKV characters, in their standard order, under the coding block "Kangxi radicals", while their graphic variants are contained in the "CJK Radicals Supplement". Thus, a reference to "radical 61", for example, without additional context, refers to the 61st radical of the Kangxi Dictionary, 心; xīn "heart". Originally introduced in the 1615 Zihui (字彙), they are more commonly named in relation to the Kangxi Dictionary of 1716 (Kāngxī 康熙 being the era name for 1662–1723). The 1915 encyclopedic word dictionary Ciyuan (辭源) also uses this system. In modern times, many dictionaries that list Traditional Chinese head characters continue to use this system. For example, the Wang Li Character Dictionary of Ancient Chinese (王力古漢語字典, 2000) adopted the Kangxi radicals system. The system of 214 Kangxi radicals is based on the older system of 540 radicals used in the Han-era Shuowen Jiezi. Since 2009, the PRC government has promoted a 201-radical system (Table of Han Character Radicals, 汉字部首表) as a national standard for Simplified Chinese (see list of Xinhua Zidian radicals).

3.8K
22 Nov 2022

Topic Review

Fragment Identifier

In computer hypertext, a fragment identifier is a string of characters that refers to a resource that is subordinate to another, primary resource. The primary resource is identified by a Uniform Resource Identifier (URI), and the fragment identifier points to the subordinate resource. The fragment identifier introduced by a hash mark # is the optional last part of a URL for a document. It is typically used to identify a portion of that document. The generic syntax is specified in RFC 3986. The hash-mark separator in URIs is not part of the fragment identifier.

3.8K
30 Nov 2022

Topic Review

Karhunen–Loève Theorem

In the theory of stochastic processes, the Karhunen–Loève theorem (named after Kari Karhunen and Michel Loève), also known as the Kosambi–Karhunen–Loève theorem is a representation of a stochastic process as an infinite linear combination of orthogonal functions, analogous to a Fourier series representation of a function on a bounded interval. The transformation is also known as Hotelling transform and eigenvector transform, and is closely related to principal component analysis (PCA) technique widely used in image processing and in data analysis in many fields. Stochastic processes given by infinite series of this form were first considered by Damodar Dharmananda Kosambi. There exist many such expansions of a stochastic process: if the process is indexed over [a, b], any orthonormal basis of L2([a, b]) yields an expansion thereof in that form. The importance of the Karhunen–Loève theorem is that it yields the best such basis in the sense that it minimizes the total mean squared error.

3.7K
08 Nov 2022

Topic Review

Epiphany (Feeling)

An epiphany (from the ancient Greek ἐπιφάνεια, epiphanea, "manifestation, striking appearance") is an experience of a sudden and striking realization. Generally the term is used to describe scientific breakthrough, religious or philosophical discoveries, but it can apply in any situation in which an enlightening realization allows a problem or situation to be understood from a new and deeper perspective. Epiphanies are studied by psychologists and other scholars, particularly those attempting to study the process of innovation. Epiphanies are relatively rare occurrences and generally follow a process of significant thought about a problem. Often they are triggered by a new and key piece of information, but importantly, a depth of prior knowledge is required to allow the leap of understanding. Famous epiphanies include Archimedes's discovery of a method to determine the volume of an irregular object ("Eureka!") and Isaac Newton's realization that a falling apple and the orbiting moon are both pulled by the same force.

3.7K
30 Nov 2022

Topic Review

Single-Speed Bicycle

A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle. There are many types of modern single speed bicycles; BMX bicycles, most bicycles designed for children, cruiser type bicycles, classic commuter bicycles, unicycles, bicycles designed for track racing, fixed-gear road bicycles, and single-speed mountain and cyclocross bikes. Although most fixed-gear bicycles (fixies) are technically single speed, the term single-speed generally refers to a single gear ratio bicycle with a freewheel mechanism to allow it to coast.

3.7K
20 Oct 2022

Topic Review

Secure Shell Protocol

The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH. SSH provides a secure channel over an unsecured network by using a client–server architecture, connecting an SSH client application with an SSH server. The protocol specification distinguishes between two major versions, referred to as SSH-1 and SSH-2. The standard TCP port for SSH is 22. SSH is generally used to access Unix-like operating systems, but it can also be used on Microsoft Windows. Windows 10 uses OpenSSH as its default SSH client and SSH server. SSH was designed as a replacement for Telnet and for unsecured remote shell protocols such as the Berkeley rsh and the related rlogin and rexec protocols. Those protocols send information, notably passwords, in plaintext, rendering them susceptible to interception and disclosure using packet analysis. The encryption used by SSH is intended to provide confidentiality and integrity of data over an unsecured network, such as the Internet.

3.7K
29 Sep 2022

Topic Review

The WannaCry ransomware attack was a worldwide cyberattack in May 2017 by the WannaCry ransomware cryptoworm, which targeted computers running the Microsoft Windows operating system by encrypting data and demanding ransom payments in the Bitcoin cryptocurrency. It propagated through EternalBlue, an exploit developed by the United States National Security Agency (NSA) for older Windows systems. EternalBlue was stolen and leaked by a group called The Shadow Brokers a month prior to the attack. While Microsoft had released patches previously to close the exploit, much of WannaCry's spread was from organizations that had not applied these, or were using older Windows systems that were past their end-of-life. These patches were imperative to organizations' cyber security but many were not implemented due to ignorance of their importance. Some have claimed a need for 24/7 operation, aversion to risking having formerly working applications breaking because of patch changes, lack of personnel or time to install them, or other reasons. The attack began at 07:44 UTC on 12 May 2017 and was halted a few hours later at 15:03 UTC by the registration of a kill switch discovered by Marcus Hutchins. The kill switch prevented already infected computers from being encrypted or further spreading WannaCry. The attack was estimated to have affected more than 200,000 computers across 150 countries, with total damages ranging from hundreds of millions to billions of United States dollar . Security experts believed from preliminary evaluation of the worm that the attack originated from North Korea or agencies working for the country. In December 2017, the United States and United Kingdom formally asserted that North Korea was behind the attack. A new variant of WannaCry forced Taiwan Semiconductor Manufacturing Company (TSMC) to temporarily shut down several of its chip-fabrication factories in August 2018. The virus spread to 10,000 machines in TSMC's most advanced facilities.

3.6K
23 Oct 2022

Topic Review

Erowid, also called Erowid Center, is a 501(c)(3) non-profit educational organization that provides information about psychoactive plants and chemicals as well as activities and technologies that can produce altered states of consciousness such as meditation, lucid dreaming, transcranial magnetic stimulation, and electroceuticals. Erowid documents legal and illegal substances, including their intended and adverse effects. Information on Erowid's website is gathered from diverse sources including published literature, experts in related fields, and the experiences of the general public. Erowid acts as a publisher of new information as well as a library for the collection of documents and images published elsewhere.

3.6K
09 Oct 2022

Topic Review

Windows 10 Version History (Version 1809)

The Windows 10 October 2018 Update (also known as version 1809 and codenamed "Redstone 5") is the sixth major update to Windows 10 and the fifth in a series of updates under the Redstone codenames. It carries the build number 10.0.17763.

3.6K
08 Nov 2022

Topic Review

IEEE 802.11ax-2021

IEEE 802.11ax-2021 or 802.11ax is an IEEE standard for wireless local-area networks (WLANs) and the successor of 802.11ac. It is marketed as Wi-Fi 6 (2.4 GHz and 5 GHz) and Wi-Fi 6E (6 GHz) by the Wi-Fi Alliance. It is also known as High Efficiency Wi-Fi, for the overall improvements to Wi-Fi 6 clients under dense environments. It is designed to operate in license-exempt bands between 1 and 7.125 GHz, including the 2.4 and 5 GHz bands already in common use as well as the much wider 6 GHz band (5.925–7.125 GHz in the US). The main goal of this standard is enhancing throughput-per-area[lower-alpha 1] in high-density scenarios, such as corporate offices, shopping malls and dense residential apartments. While the nominal data rate improvement against 802.11ac is only 37%,:qt the overall throughput improvement (over an entire network) is 400% (hence High Efficiency).:qt This also translates to 75% lower latency. The quadruplication of overall throughput is made possible by a higher spectral efficiency. The key feature underpinning 802.11ax is orthogonal frequency-division multiple access (OFDMA), which is equivalent to cellular technology applied into Wi-Fi.:qt Other improvements on spectrum utilization are better power-control methods to avoid interference with neighboring networks, higher order 1024‑QAM, up-link direction added with the down-link of MIMO and MU-MIMO to further increase throughput, as well as dependability improvements of power consumption and security protocols such as Target Wake Time and WPA3. The IEEE 802.11ax-2021 standard was approved in February 9th, 2021.

3.6K
11 Nov 2022

Topic Review

In recreational number theory, a unique prime or unique period prime is a certain kind of prime number. A prime p ≠ 2, 5 is called unique if there is no other prime q such that the period length of the decimal expansion of its reciprocal, 1 / p, is equal to the period length of the reciprocal of q, 1 / q. For example, 3 is the only prime with period 1, 11 is the only prime with period 2, 37 is the only prime with period 3, 101 is the only prime with period 4, so they are unique primes. In contrast, 41 and 271 both have period 5; 7 and 13 both have period 6; 239 and 4649 both have period 7; 73 and 137 both have period 8; 21649 and 513239 both have period 11; 53, 79 and 265371653 all have period 13; 31 and 2906161 both have period 15; 17 and 5882353 both have period 16; 2071723 and 5363222357 both have period 17; 19 and 52579 both have period 18; 3541 and 27961 both have period 20. Therefore, none of these is a unique prime. Unique primes were first described by Samuel Yates in 1980. The above definition is related to the decimal representation of integers. Unique primes may be defined and have been studied in any numeral base.

3.6K
20 Oct 2022

Topic Review

Structuralism (Philosophy of Science)

Structuralism[α] (also known as scientific structuralism or as the structuralistic theory-concept) asserts that all aspects of reality are best understood in terms of empirical scientific constructs of entities and their relations, rather than in terms of concrete entities in themselves. Structuralism is an active research program in the philosophy of science, which was first developed in the late 1960s and throughout the 1970s by several analytic philosophers.

3.6K
23 Nov 2022

Topic Review

Gendered Associations of Pink and Blue

The colors pink and blue are associated with girls and boys respectively, in the United States, the United Kingdom and some other European countries. Originating as a trend in the mid-19th century and applying primarily to clothing, gendered associations with pink and blue became more widespread from the 1950s onward. Since the 1990s, these gendered associations have also increasingly applied to toys as well, especially in the case of pink toys for girls. Despite popular belief—including from various academic and popular sources—a reported "pink-blue reversal", wherein the gendered associations of both colors were "flipped" sometime during the 20th century, most likely never occurred, and instead is likely to have been a misunderstanding of earlier reporting.

3.6K
19 Oct 2022

Topic Review

Malfatti Circles

In geometry, the Malfatti circles are three circles inside a given triangle such that each circle is tangent to the other two and to two sides of the triangle. They are named after Gian Francesco Malfatti, who made early studies of the problem of constructing these circles in the mistaken belief that they would have the largest possible total area of any three disjoint circles within the triangle. Malfatti's problem has been used to refer both to the problem of constructing the Malfatti circles and to the problem of finding three area-maximizing circles within a triangle. A simple construction of the Malfatti circles was given by (Steiner 1826), and many mathematicians have since studied the problem. Malfatti himself supplied a formula for the radii of the three circles, and they may also be used to define two triangle centers, the Ajima–Malfatti points of a triangle. The problem of maximizing the total area of three circles in a triangle is never solved by the Malfatti circles. Instead, the optimal solution can always be found by a greedy algorithm that finds the largest circle within the given triangle, the largest circle within the three connected subsets of the triangle outside of the first circle, and the largest circle within the five connected subsets of the triangle outside of the first two circles. Although this procedure was first formulated in 1930, its correctness was not proven until 1994.

3.6K
09 Oct 2022

Topic Review

Calibre (/ˈkælɪbər/, stylised calibre) is a cross-platform free and open-source suite of e-book software. Calibre supports organizing existing e-books into virtual libraries, displaying, editing, creating and converting e-books, as well as syncing e-books with a variety of e-readers. Editing books is supported for EPUB and AZW3 formats. Books in other formats like MOBI must first be converted to those formats, if they are to be edited.

3.6K
20 Oct 2022

Topic Review

In computational linguistics and computer science, edit distance is a way of quantifying how dissimilar two strings (e.g., words) are to one another by counting the minimum number of operations required to transform one string into the other. Edit distances find applications in natural language processing, where automatic spelling correction can determine candidate corrections for a misspelled word by selecting words from a dictionary that have a low distance to the word in question. In bioinformatics, it can be used to quantify the similarity of DNA sequences, which can be viewed as strings of the letters A, C, G and T. Different definitions of an edit distance use different sets of string operations. Levenshtein distance operations are the removal, insertion, or substitution of a character in the string. Being the most common metric, the term Levenshtein distance is often used interchangeably with edit distance.

3.5K
02 Dec 2022

Topic Review

Burnin' Rubber (Series)

Burnin' Rubber is a series of vehicular combat racing video games developed by Xform and published by various companies. The series has appeared on AirConsole, Android, Browser, IOS, and Microsoft Windows. The gameplay mainly focuses on the player having to beat a set of challenges ranging from races, boss battles, and time trials. Players can gain various pickups and collectables placed throughout tracks to aid them in the event and unlock new content. The series previous used Adobe Director and Adobe Shockwave Player for its games and has since migrated to Unity. Burnin' Rubber 3 was the first game in the series to introduce the addition of weapons in which the player can add to their vehicles which would become one of the game's main element moving forward. Excluding Burnin' Rubber (2007), the vehicles can receive damage or explode once critical damage levels has been surpassed. The series takes some inspiration from the Burnout series.

3.5K
26 Oct 2022

Topic Review

Cortana is a virtual assistant developed by Microsoft which uses the Bing search engine to perform tasks such as setting reminders and answering questions for the user. Cortana is currently available in English, Portuguese, French, German, Italian, Spanish, Chinese, and Japanese language editions, depending on the software platform and region in which it is used. Microsoft began reducing the prevalence of Cortana and converting it from an assistant into different software integrations in 2019. It was split from Windows 10's search bar in April 2019. In January 2020, Cortana mobile app was removed from certain markets and in first half of 2021 Cortana mobile app was shut down globally.

3.5K
24 Oct 2022

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