Google+ bgs: 7 Jun 2011
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What is CAPTCHA and How it Works?

CAPTCHA or Captcha (pronounced as cap-ch-uh) which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart” is a type of challenge-response test to ensure that the response is only generated by humans and not by a computer. In simple words, CAPTCHA is the word verification test that you will come across the end of a sign-up form while signing up for Gmail or Yahoo account. The following image shows the typical samples of CAPTCHA.

Almost every Internet user will have an experience of CAPTCHA in their daily Internet usage, but only a few are aware of what it is and why they are used. So in this post you will find a detailed information on how CAPTCHA works and why they are used.
What Purpose does CAPTCHA Exactly Serve?
CAPTCPA is mainly used to prevent automated software (bots) from performing actions on behalf of actual humans. For example while signing up for a new email account, you will come across a CAPTCHA at the end of the sign-up form so as to ensure that the form is filled out only by a legitimate human and not by any of the automated software or a computer bot. The main goal of CAPTCHA is to put forth a test which is simple and straight forward for any human to answer but for a computer, it is almost impossible to solve.
What is the Need to Create a Test that Can Tell Computers and Humans Apart?
For many the CAPTCHA may seem to be silly and annoying, but in fact it has the ability to protect systems from malicious attacks where people try to game the system. Attackers can make use of automated softwares to generate a huge quantity of requests thereby causing a high load on the target server which would degrade the quality of service of a given system, whether due to abuse or resource expenditure. This can affect millions of legitimate users and their requests. CAPTCHAs can be deployed to protect systems that are vulnerable to email spam, such as the services from Gmail, Yahoo and Hotmail.
Who Uses CAPTCHA?
CAPTCHAs are mainly used by websites that offer services like online polls and registration forms. For example, Web-based email services like Gmail, Yahoo and Hotmail offer free email accounts for their users. However upon each sign-up process, CAPTCHAs are used to prevent spammers from using a bot to generate hundreds of spam mail accounts.
Designing a CAPTCHA System
CAPTCHAs are designed on the fact that computers lack the ability that human beings have when it comes to processing visual data. It is more easily possible for humans to look at an image and pick out the patterns than a computer. This is because computers lack the real intelligence that humans have by default. CAPTCHAs are implemented by presenting users with an image which contains distorted or randomly stretched characters which only humans should be able to identify. Sometimes characters are striked out or presented with a noisy background to make it even more harder for computers to figure out the patterns.
Most, but not all, CAPTCHAs rely on a visual test. Some Websites implement a totally different CAPTCHA system to tell humans and computers apart. For example, a user is presented with 4 images in which 3 contains picture of animals and one contain a flower. The user is asked to select only those images which contain animals in them. This Turing test can easily be solved by any human, but almost impossible for a computer.
Breaking the CAPTCHA
The challenge in breaking the CAPTCHA lies in real hard task of teaching a computer how to process information in a way similar to how humans think. Algorithms with artificial intelligence (AI) will have to be designed in order to make the computer think like humans when it comes to recognizing the patterns in images. However there is no universal algorithm that could pass through and break any CAPTCHA system and hence each CAPTCHA algorithm must have to be tackled individually. It might not work 100 percent of the time, but it can work often enough to be worthwhile to spammers.

Top 25 Android apps: The best of the best

The Android Market may not have as many apps as the iPhone App Store yet, but there are still enough to be overwhelmed, and it’s growing at a breakneck pace. To help you sort through them all, here’s my list of the best apps I’ve found on Android. Again, remember that this is a snapshot in time. The Android platform is developing so quickly right now that I guarantee my home screen look different a month from now.  However, you can also view top 25 in the list below.

The list

1. Google Voice

Google Voice is a service that is so useful I consider it one of the top benefits of Android itself, especially since Apple rejected the Google Voice app for the iPhone. It gives you a phone number that can ring to multiple places or devices and it allows you to access all of your voicemail and text messages over the Web. The Android app integrates even deeper. It can make outgoing calls look like they’re coming from your Google Voice number so that you can keep your real mobile number private.

2. Advanced Task Killer

One of the realities of having a multitasking mobile OS in Android is that you have to manage your apps so that they don’t hurt performance or battery life. Advanced Task Killer (or ATK) is my favorite. It even comes with a widget that you can tap once to kill all open apps.

3. Dropbox

Dropbox is a great cloud service that automatically syncs a folder of files between multiple computers (Windows, Mac, or Linux). This app extends Dropbox to Android and interacts with other apps (such as Documents To Go) to open the files.

4. Evernote

Once you get used to typing on a virtual keyboard (and it honestly took me over a year to do it), then these devices are great for note-taking, and Evernote is a great note-taking app. It is similar to Dropbox in that it saves data locally but syncs it across all your machines and devices.

5. DroidAnalytics

For some reason Google doesn’t have an official app (for either Android or iPhone) for Google Analytics. The best one I’ve found on Android is DroidAnalytics. Another good one is mAnalytics.

6. Documents To Go

The free version of Documents To Go offers a great little reader for Word and Excel files. You can upgrade to the full version (for $15) if you want to edit files and add PowerPoint files to the mix. If you do want editing capability, I’d also recommend taking a look at QuickOffice.

7. Amazon Kindle

I never warmed up to the Amazon Kindle e-reader, but I’m a big fan of the Kindle mobile app. Since it was released I’ve read a lot more books simply because my smartphone is always with me and I can pull it and read a few pages anytime I’ve got a couple minutes free.

8. Places Directory

This is an awesome app for finding shops and services near your current location. From restaurants to movie theaters to medical facilities to taxis, this app is very accurate and takes advantage of the business information from Google Local. This app is better than the info you get from a GPS unit (or app) and better than any of the similar apps available on the iPhone.

9. Tripit

I dig Tripit. It is by far the best app I’ve found for keeping track of all my travel itineraries. It runs on some great backend systems. You simply forward your confirmation emails for your flights, hotels, rental cars, and more to Tripit and it automatically organizes them into trips with all your details and confirmation numbers.

10. Seesmic

Twitter is an amazing instant-intelligence engine and it was made for mobile browsing. Although there’s an official Twitter app for Android now, Seesmic is still the best Android Twitter client.

11. FCC Speedtest

I’m obsessed with running speed tests to check my bandwidth in various places, both to see 3G fluctuations and to check the quality of Wi-Fi. There are a number of really good speedtest apps, but my new favorite is the FCC Test app.

12. Astro File Manager

Another one of the great things about Android (if you’re a geek or a tinkerer) is that you have lower-level access to the system itself. Astro is an app that lets you navigate the Android file system.

13. Got To Do

There are plenty of to-do apps to choose from on Android but I prefer Got To Do because of the solid interface and the fact that it can sync with the online service Toodledo.

14. Gist

Many of us have contact lists scattered across various computers, devices, and online services. Gist is a Web service that can bring them together and even pull in stuff from the Web to help you stay up to date with your most important contacts. There’s an Android app as well as an iPhone app.

15. TED Mobile

TED is a fascinating event that features a meeting of the minds of some of society’s most influential thinkers. You’ll definitely disagree with some of them, because there’s a large diversity of opinions, but many talks are worth listening to. What I love is that they’ve taken the videos from their conference and made them freely available on the Web. This app provides a great way to access the videos. I hope more conferences follow TED’s lead on this.

16. Pandora

Pandora is a streaming “radio station” for the Internet age. You simply search by an artist or song and it will create a running playlist based on that one piece of information. It intersperses an occasional ad between songs but the ads tend to be fairly localized and occasionally even useful.

17. Shazam

If you want to impress your friends with a mobile app, show them Shazam. Ever hear a song being played at a store or on the radio and ask yourself, “Oh, what song is that?” That’s where Shazam comes in. Just hit the button and let it listen for 15 seconds, query its database, and then return the name of artist and the song. It has about an 80% success rate.

18. Dial Zero

Are you one of those people who dials a customer service line and just keeps pressing zero until you get to talk to a real person? Then Dial Zero is your new friend. This app provides a directory of a ton of U.S. businesses and gives you numbers to help you get closer to a real person and instructions for which prompts to hit to speak to a human being as quickly as possible.

19. Google Goggles

This is a fun app that is a little but ahead of its time. It does visual searches. You can take pictures of things and then the app tries to tell you what they are. It’s limited in its scope but it is pretty cool, and it’s definitely a peek into the future. One of the coolest features is the ability to take pictures of text in a foreign language and let that app translate for you. In a foreign country, this can help you read street signs and avoid going into the wrong bathroom. :-)

20. Google Sky Map

Ever look up at the night sky and try to tell your kids the name of that constellation you’re pointing at, or try to remember which planet that is in the southern sky? Google SkyMap lets you point your smartphone at it and get the information. This is part of a new breed of apps called “Augmented Reality” apps that layer digital information on top of real world experiences.

21. Tricorder

A lot of geeks I know like to say that our smartphones are becoming more and more like the Tricorders on Star Trek. Well, here’s a fun app that turns your Android device into a virtual Tricorder. It even offers some useful environmental information, including GPS data, wireless data, and ambient sound measurements.

22. FxCamera

Honestly, the camera software on Android is an area where major improvements are needed, but this app is a great example of what’s possible. It has solid camera controls, full customization options, and offers some great effects for photos.

23. Photoshop Mobile

Photoshop is, of course, the best known photo editor in the world and its mobile app doesn’t do anything to hurt that reputation. But while the desktop version is know for having a zillion features, the mobile app is distinguished by its simplicity. It’s the best Android (and iPhone) photo editing app for simple crops, brightness adjustments, and sharpens, for example.

24. Bump

Bump is a fun (and useful) idea for sharing info between two phones using the accelerometer, and it works across Android and iPhone. You can use it to share contact info (yours and others), photos, and apps. You both simply open the Bump app, choose what you to share, and then hold the phones in your hands and bump your hands together.

25. Barcode Scanner

This app turns the Android camera into a barcode scanner. You simply scan a product’s UPC code and let the app go to work to find it in Google Product Search or a search on the open Web. You’ll be amazed at how fast it works. This is great for when you’re shopping retail and you want to check the price of a product online before buying to make sure you’re paying a fair price.

How to Check if your Mac Malware Definitions List is Updated

Are you wondering how to check your Mac Malware definitions list is updated or not? Well, Apple has released Mac OS X Security Update to protect Mac from malware. Mac OS X security update automatically download and update it’s malware definitions list from Apple. If you want to know how to manually check if the list is updated or not then simply follow the steps  posted below using which you can manually check whether the list is updated or not.

How to Check if your Mac Malware Definitions List is Updated

STEP 1. First you have to launch the Terminal of Mac OS X.

STEP 2. Now you have to paste the command given below in the Terminal of Mac OS X:

cat /System/Library/CoreServices/CoreTypes.bundle/Contents/Resourses/XProtect.meta.plist
STEP 3. Now simply look at the data entry between the string tags, as shown in the image below:

Check Mac Malware Definitions List

The integer tag shows which version the definitions list is and the date listed shows when the file was last modified. In this way you can manually check whether the Malware definitions list of your Mac is updated or not.

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