Computer Security

Computer security is a branch of computer technology known as Information Security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to remain accessible and productive to its intended users. The term computer system security means the collective processes and mechanisms by which sensitive and valuable information and services are protected from publication, tampering or collapse by unauthorized activities or untrustworthy individuals and unplanned events respectively. The strategies and methodologies of computer security often differ from most other computer technologies because of its somewhat elusive objective of preventing unwanted computer behavior instead of enabling wanted computer behavior. Security Architecture can be defined as the design artifacts that describe how the security controls (security countermeasures) are positioned, and how they relate to the overall information technology architecture. These controls serve the purpose to maintain the system's quality attributes, among them confidentiality, integrity, availability, accountability and assurance. The technologies of computer security are based on logic. As security is not necessarily the primary goal of most computer applications, designing a program with security in mind often imposes restrictions on that program's behavior. There are 4 approaches to security in computing; sometimes a combination of approaches is valid: Trust all the software to abide by a security policy but the software is not trustworthy (this is computer insecurity). Trust all the software to abide by a security policy and the software is validated as trustworthy (by tedious branch and path analysis for example). Trust no software but enforce a security policy with mechanisms that are not trustworthy (again this is computer insecurity). Trust no software but enforce a security policy with trustworthy hardware mechanisms. Many systems have unintentionally resulted in the first possibility. Since approach two is expensive and non-deterministic, its use is very limited. Approaches one and three lead to failure. Because approach number four is often based on hardware mechanisms and avoids abstractions and a multiplicity of degrees of freedom, it is more practical. Combinations of approaches two and four are often used in a layered architecture with thin layers of two and thick layers of four. There are various strategies and techniques used to design security systems. However, there are few, if any, effective strategies to enhance security after design. One technique enforces the principle of least privilege to great extent, where an entity has only the privileges that are needed for its function. That way even if an attacker gains access to one part of the system, fine-grained security ensures that it is just as difficult for them to access the rest. Furthermore, by breaking the system up into smaller components, the complexity of individual components is reduced, opening up the possibility of using techniques such as automated theorem proving to prove the correctness of crucial software subsystems. This enables a closed form solution to security that works well when only a single well-characterized property can be isolated as critical, and that property is also assessable to math. Not surprisingly, it is impractical for generalized correctness, which probably cannot even be defined, much less proven. Where formal correctness proofs are not possible, rigorous use of code review and unit testing represent a best-effort approach to make modules secure. The design should use "defense in depth", where more than one subsystem needs to be violated to compromise the integrity of the system and the information it holds. Defense in depth works when the breaching of one security measure does not provide a platform to facilitate subverting another. Also, the cascading principle acknowledges that several low hurdles does not make a high hurdle. So cascading several weak mechanisms does not provide the safety of a single stronger mechanism. Subsystems should default to secure settings, and wherever possible should be designed to fail secure rather than fail insecure. Ideally, a secure system should require a deliberate, conscious, knowledgeable and free decision on the part of legitimate authorities in order to make it insecure. In addition, security should not be an all or nothing issue. The designers and operators of systems should assume that security breaches are inevitable. Full audit trails should be kept of system activity, so that when a security breach occurs, the mechanism and extent of the breach can be determined. Storing audit trails remotely, where they can only be appended to, can keep intruders from covering their tracks. Finally, full disclosure helps to ensure that when bugs are found the "window of vulnerability is kept as short as possible.

City Car

A city car is a small, moderately powered automobile intended for use in urban areas. It has four seats, they are typically between 3.4 m and 3.6 m long. These cars have been sold in Europe since the 1960s, and now are an official car classification. Most mainstream manufacturers have one or even two city cars in their lineup. The city car's greater speed and occupant protection allow relatively safe operation in mixed traffic environments and in all weather conditions. One of the earliest city cars was the American-made Crosley, a four passenger vehicle from the late 1940's. While many cars of the 1960s are small enough to be considered city cars today, these cars have been replaced by larger cars with each passing generation. Exceptions are the smaller Fiats, especially the Fiat 500 and Fiat 126. They were in the region of 3.0 meters in length, but had seating for four people, putting them outside the micro car category. wiki city car In the late 1980s superminis had grown so much that many buyers wanted even smaller four-seat cars. Renault followed Fiat in 1993 with the Renault Twingo, which featured a MPV-like design and interior room, despite its size and height (3430 mm long and 1420 mm tall). Combined with an original exterior and interior design, it quickly became a best-seller. In 1996 the Ford Ka was presented with its radical New Edge design. Its egg-shaped body did not leave much room in the rear seats, but many customers did not need them and preferred the Ka over more conservative designs.

In the mid 1990s, South Korean brands Daewoo and Hyundai introduced their city car entries, both for the Asian and European markets. The Hyundai Atos, launched in 1997, was 3500 mm long and 1600 mm high, which was much taller than any European models (usually under 1450 mm) and provided considerable interior space. Its boxy shape provoked mixed reactions.

The Daewoo Matiz followed in 1998 with a Giorgetto Giugiaro design and a moderate height (1500 mm), which proved more eye-catching. Hyundai tried to react to this with the rounder Atos Prime but without much success.

These Korean city cars were much cheaper than most of the European models, especially the Opel Agila (2000) and Volkswagen Lupo (1999), yet were still reliable. However, sales were dominated by the Renault Twingo and Ford Ka.

City car / supermini crossovers

While small family cars and superminis grew considerably from the 1990s to the 2000s, so happened with city cars. After some new superminis were over 3900 mm long (like the Ford Fiesta, the SEAT Ibiza, Maruti Alto and the Volkswagen Polo) some automakers designed models above 3650 mm long.

The first of these models was the Nissan Micra (2002), which is 3720 mm long and smaller that many superminis of the late 1990s. Other cars are the Citroën C2, Suzuki Swift, Smart Forfour, Toyota Yaris and Peugeot 1007 (the last one which can also be labelled as a mini MPV). These vehicles are hard to classify, since their size does not fit the "city car" or "supermini" categories. A possibility is to compare the price and interior room with superminis: the Yaris is definitely a supermini, whereas the Tata Indica is closer to a city car. In addition, in the last few years some "true" city cars were released, like the Fiat Panda (2003), the Kia Picanto (2004) and the Citroën C1/Peugeot 107/Toyota Aygo trio. Other mainstream European manufacturers will release all-new models in 2007: the Renault Twingo, Fiat Nuova 500 and the Ford Ka.

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