viernes, 23 de noviembre de 2012
martes, 13 de noviembre de 2012
jueves, 8 de noviembre de 2012
viernes, 26 de octubre de 2012
martes, 9 de octubre de 2012
lunes, 24 de septiembre de 2012
Star topology network
Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer, which acts as a conduit to transmit messages. This consists of a central node, to which all other nodes are connected; this central node provides a common connection point for all nodes through a hub.
Ringo Topology Network
In a ring network, every device has exactly two neighbors for
communication purposes . All messages travel through a ring in the
same direction (effectively either "clockwise" or "counterclockwise"). A
failure in any cable or device breaks the loop and can take down the
entire network.
To implement a ring network we use theToken Ring technology. A Token is
passed from one computer to another which enables each computer to have
equal access to the network.
Bus Topology network
A bus network topology is a network architecture in which a set of clients are connected via a shared communications line/cables, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions of Ethernet networks.
viernes, 7 de septiembre de 2012
jueves, 6 de septiembre de 2012
jueves, 2 de agosto de 2012
viernes, 27 de julio de 2012
Hardware and software liability by Tim Tompkins
What is a end user license agreement?
Is the contract between the licensor and purchaser, establishing the purchaser's right to use the software.The user has the choice of accepting or rejecting the agreement. The
installation of the software is conditional to the user clicking a
button labelled "accept".Most commonly, a EULA will attempt to hold harmless
the software licensor in the event that the software causes damage to
the user's computer or data, but some software also proposes limitations
on whether the licensor can be held liable for damage that arises
through improper use of the software.
Do you agree or
disagree that the developer should be responsible for his or her
development of hardware or software products? Explain your answer.
Im agree because the developer have to be responsible for this own development of the hardware or software products. His work is to en charge that everything is working efficient in the system, and if something isn't working is their fault because they had not been taking charge of their work.
What are the three
levels of loss described in the article?
A second level of loss includes the cost of providing emergency service during the failure
of the primary service. Should a product fail, a temporary fix often needs to be applied
immediately to allow the customer to continue operation in a semi-normal manner, especially for
mission-critical systems in hospital, military, and numerous other important applications. Also in
this category is the cost of restoring data, should it be necessary.The third level of loss is long-term. Should a company's systems fail, either due to their
own hardware and software, or that which they have purchased or licensed from another
company, customers may no longer be willing to trust that company with their business, so the
company's long term reputation, and consequently profit, are diminished.
Should hardware and
software liability be treated the same or differently? Explain your
answer.
Both should be treated the same because this two are important to the company, and if one them is damage it would cost to the company.It is a important document that would be response and taking care of the damage in software or hardware. The hardware and software liability is a license that would make the two parts (user and company) take responsibility in a bug of the system.
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Source:
- http://www.cs.rpi.edu/academics/courses/fall00/ethics/papers/tompkt.html
- http://en.wikipedia.org/wiki/End-user_license_agreement
martes, 17 de julio de 2012
viernes, 13 de julio de 2012
CIA Gives the Soviets Gas (1982)
Problem: Control software went haywire and produced
intense pressure in the Trans-Siberian gas pipeline, resulting in the
largest man-made non-nuclear explosion in Earth’s history.
Cause: CIA operatives allegedly planted a bug in a
Canadian computer system purchased by the Soviets to control their gas
pipelines. The purchase was part of a strategic Soviet plan to steal or
covertly obtain sensitive U.S. technology. When the CIA discovered the
purchase, they sabotaged the software so that it would pass Soviet
inspection but fail in operation.
Cost: Millions of dollars, significant damage to Soviet economy
Medical Machine Kills (1985)
Problem: Canada’s Therac-25 radiation therapy machine malfunctioned and delivered lethal radiation doses to patients,that were there to cure themselves but it was all the opposite for those patients.Start affecting their cells and the immune system.
Cause: Because of a subtle bug called a race condition,
a technician could accidentally configure Therac-25 so the electron
beam would fire in high- power mode without the proper patient shielding.
Cost: Three people dead, three people critically injured.
lunes, 9 de julio de 2012
martes, 3 de julio de 2012
What are the symptoms of an infected computer?
It’s very difficult to provide a list of characteristic
symptoms of a compromised computer because the same symptoms can also be
caused by hardware and/or software problems. Here are just a few
examples:
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Your computer behaves strangely, i.e. in a way that you haven’t seen before.
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You see unexpected messages or images.
-
You hear unexpected sounds, played at random.
-
Programs start unexpectedly.
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Your personal firewall tells you that an application has tried to connect to the Internet (and it’s not a program that you ran).
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Your friends tell you that they have received e-mail messages from your address and you haven’t sent them anything.
-
Your computer ‘freezes’ frequently, or programs start running slowly.
-
You get lots of system error messages.
-
The operating system will not load when you start your computer.
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You notice that files or folders have been deleted or changed.
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You notice hard disk access (shown by one of the small flashing lights) when you’re not aware of any programs running.
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Your web browser behaves erratically, e.g. you can’t close a browser window.
http://www.kaspersky.com/symptoms
Password Guidelines
Keep it secret, Keep it safe
Choosing the right password is something that many people find difficult,
there are so many things that require passwords these days that remembering them all can
be a real problem. Perhaps because of this a lot of people choose their passwords
very badly. The simple tips below are intended to assist you in choosing a good password.I'm also starting work on a Password FAQ, which will probably replace this document.
See also my password recovery speeds page, which lists the time taken to break various passwords using brute force alone.
Basics
- Use at least eight characters, the more characters the better really, but most people will find anything more than about 15 characters difficult to remember.
- Use a random mixture of characters, upper and lower case, numbers, punctuation, spaces and symbols.
- Don't use a word found in a dictionary, English or foreign.
- Never use the same password twice.
Things to avoid
- Don't just add a single digit or symbol before or after a word. e.g. "apple1"
- Don't double up a single word. e.g. "appleapple"
- Don't simply reverse a word. e.g. "elppa"
- Don't just remove the vowels. e.g. "ppl"
- Key sequences that can easily be repeated. e.g. "qwerty","asdf" etc.
- Don't just garble letters, e.g. converting e to 3, L or i to 1, o to 0. as in "z3r0-10v3"
Tips
- Choose a password that you can remember so that you don't need to keep looking it up, this reduces the chance of somebody discovering where you have written it down.
- Choose a password that you can type quickly, this reduces the chance of somebody discovering your password by looking over your shoulder.
Bad Passwords
- Don't use passwords based on personal information such as: name, nickname, birthdate, wife's name, pet's name, friends name, home town, phone number, social security number, car registration number, address etc. This includes using just part of your name, or part of your birthdate.
- Don't use passwords based on things located near you. Passwords such as "computer", "monitor", "keyboard", "telephone", "printer", etc. are useless.
- Don't ever be tempted to use one of those oh so common passwords that are easy to remember but offer no security at all. e.g. "password", "letmein".
- Never use a password based on your username, account name, computer name or email address.
Choosing a password
- Use good password generator software.
- Use the first letter of each word from a line of a song or poem.
- Alternate between one consonant and one or two vowels to produce nonsense words. eg. "taupouti".
- Choose two short words and concatenate them together with a punctuation or symbol character between the words. eg. "seat%tree"
Changing your password
- You should change your password regularly, I suggest once a month is reasonable for most purposes.
- You should also change your password whenever you suspect that somebody knows it, or even that they may guess it, perhaps they stood behind you while you typed it in.
- Remember, don't re-use a password.
Protecting your password
- Never store your password on your computer except in an encrypted form. Note that the password cache that comes with windows (.pwl files) is NOT secure, so whenever windows prompts you to "Save password" don't.
- Don't tell anyone your password, not even your system administrator
- Never send your password via email or other unsecured channel
- Yes, write your password down but don't leave the paper lying around, lock the paper away somewhere, preferably off-site and definitely under lock and key.
- Be very careful when entering your password with somebody else in the same room.
Remembering your password
Remembering passwords is always difficult and because of this many people are tempted to write them down on bits of paper. As mentioned above this is a very bad idea. So what can you do?- Use a secure password manager, see the downloads page for a list of a few that won't cost you anything.
- Use a text file encrypted with a strong encryption utility.
- Choose passwords that you find easier to remember.
Bad Examples
- "fred8" - Based on the users name, also too short.
- "christine" - The name of the users girlfriend, easy to guess
- "kciredref" - The users name backwords
- "indescribable" - Listed in a dictionary
- "iNdesCribaBle" - Just adding random capitalisation doesn't make it safe.
- "gandalf" - Listed in word lists
- "zeolite" - Listed in a geological dictionary
- "qwertyuiop" - Listed in word lists
- "merde!" - Listed in a foreign language dictionary
Good Examples
None of these good examples are actually good passwords, that's because they've been published here and everybody knows them now, always choose your own password don't just use somebody elses.- "mItWdOtW4Me" - Monday is the worst day of the week for me.
miércoles, 30 de mayo de 2012
lunes, 28 de mayo de 2012
Samsung Galaxy SII
viernes, 18 de mayo de 2012
Maker of Angry Birds Shows Way for European Start-Ups
PARIS — As Silicon Valley prepares for its latest blockbuster initial public offering, a sale of stock that is expected to value Facebook at more than $100 billion, Europe can counter with the David and Goliath tale of Rovio Entertainment.
The company, developer of the “Angry Birds” games, in which players use a digital slingshot to attack egg-stealing pigs, has said it plans its own offering next year. Analysts have said the sale could value Rovio, which is based in Finland, at up to $9 billion — a small fraction of Facebook’s valuation, but huge for a European technology I.P.O.
The recent success of Rovio and a handful of other emerging European Internet companies, including Spotify, the online music streaming service, and SoundCloud, an audio sharing platform, shows that Europe can deliver innovation on a global scale. No longer are European Internet companies merely copying Silicon Valley business models, something for which they were long criticized, especially during the dot-com bubble years.
“Now you’ve got European entrepreneurs that have figured out how to build category leaders, not just clones,” said Jason Whitmire, a partner at Earlybird Venture Capital, which is active in Germany and elsewhere in Europe. “That wasn’t happening 10 years ago.”
Analysts say Rovio’s success may also offer policy makers useful lessons in how to stimulate the Internet and technology scene. In general, however, start-ups in Europe often struggle to get off the ground, finding it harder to raise money at the critical early stages than their American counterparts.
Finland has lagged behind other European countries in putting in place financial incentives, like tax breaks, for start-ups. Other factors, analysts say, have been more important in fostering the growth of high-technology ventures like Rovio.
One is creative destruction of a kind celebrated by the economist Joseph Schumpeter. Rovio is based in the same city, Espoo, as Nokia, the struggling mobile phone maker that used to be the pride of the Finnish high-technology sector. As the company loses market share, it has responded by shedding thousands of jobs — a ready pool of engineering talent for entrepreneurs to tap.
“The important thing is that the way people think has changed, especially young people,” said Artturi Tarjanne, general partner at Nexit Ventures in Helsinki. “They used to dream about going to work for Nokia or McKinsey or something like that. Now they are much more willing to take entrepreneurial risk.”
Another vibrant European startup center, Berlin, also shows it is sometimes the things that policy makers do not do that can be most effective in luring Internet entrepreneurs. While France and Britain, for example, have put in place tax breaks to support venture investments, Germany has not followed suit.
Over the past year, however, U.S. venture capital commitments to Berlin firms have roughly tripled, Mr. Whitmire at Earlybird estimated. Big players in Silicon Valley, like Sequoia Capital, Tiger Global Management and Kleiner Perkins Caufield & Byers have all made Berlin investments.
Instead of financial incentives, Berlin has benefited from other factors, like an influx of engineers from Eastern Europe. Low rents have helped cash-strapped company founders eke out an existence. Meanwhile, analysts say Berlin has also benefited from tougher immigration rules in Britain, which have made it more difficult for start-ups and technology giants alike to add jobs in London, Berlin’s biggest rival on the European Internet scene.
“While there are certain things that government can do, to a large extent it should stand out of the way,” said Paul Zwillenberg, a partner at Boston Consulting Group.
As for Rovio, it plays down the challenges facing start-ups in Europe, compared with their counterparts in the United States. The company recently attracted a $42 million investment from a group of firms led by a big player in Silicon Valley, Accel Partners.
“You might say that the culture is somewhat different,” said Mikael Hed, chief executive of Rovio, via e-mail. “But at the end of the day dynamic businesses have the ability to attract venture capital no matter where they’re located.”
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