Breaking CAPTCHA: Getting Naughty with Computer Vision……. And Captcha Breaking Experiment in PHP…. These terms now familiar to us. 1st one was made possible by Nadim vai and 2nd one by M. M. Rifat-Un-Nabi. Their post makes me inspire to get naughty once again more simply and more easily. Because I like simplicity ;). I also choosed SomeWhereInDhaka.Net Captcha to do this experiment.
The SomeWhereInDhaka.Net CAPTCHA suffers several weaknesses: fixed font face, fixed font size, no distortions and it’s easy to segment. In this experiment, I have developed simple algorithm to break the SomeWhereInDhaka.Net CAPTCHA.
- At first need the captcha image from the page, We can do it in two way :
(a) capturing only the captcha portion [I have used php function: imagejpeg()] or,
(b) capturing the page image by php function and then crop only captcha portion from that page.
- So, we got that captcha. Now sampling that captcha image
- Match sampling pattern with reference pattern. If matching is true then it will give output, In this case the captcha value. (No need any edit distance algorithm)
You can see the effect here.
I post my website ads 😛 as spam. So, isn’t it more simple.
And finally a sympathy will goes for SomeWhereInDhaka.Net. And also I would like to thanks them because they not change there captcha yet. and it help me to make this experiment :D. So, my friends if wana see weak captcha then what are you waiting for – just log in to SomeWhereInDhaka.Net and keep getting naughty :P.
Google.com , everybody knows about this site. This is an American public corporation which main source of revenue is online advertising. If anybody asked which service of google is most popular then without any confusion you can answer google search engine.
Actually now-a-days if we need any information’s, any songs ,topics then we search in google. Its very interesting that
how google search a huge database and give relatively desire output with in a second.
In addition to providing easy access to billions of web pages, Google has many special features to help you to find exactly what we’re looking for. An important feature is Google Cache.
Now before discuss about google cache lets see about cache. What is Cache?
Actually Cache is a process of data or information backup where original data or information source is expensive to fetch and will kill time. Once the data is stored in the cache, in future we can use that data with out refetching original data which will consume our average access time.
Now what about Google Cache ? Google takes a snapshot of each page it examines and caches (stores) that version as a back-up. The cached version is what Google uses to judge if a page is a good match for our query. Google indexes a page (adds it to its index and caches it) frequently if the page is popular (has a high PageRank) and if the page is updated regularly. The new cached version replaces any previous cached versions of the page. Users can access the cached version by choosing the “Cached” link on the search results page.
A few days ago I have faced a peculiar problem. My homepage, which was http://www.engr-faisal.co.cc. I have converted that site in XHTML and change site URL in www.engr-faisal.co.nr. And older site has closed and the link is not available. But it still showing in google cache. So, this little bit bothering me. So, for preventing this type of problem we can follow ………
To prevent all search engines from showing a “Cached” link for your site, place this tag in the section of your page:
<meta name=”robots” content=”noarchive”>
To allow other search engines to show a “Cached” link, preventing only Google from displaying one, use the following tag:
<meta name=”googlebot” content=”noarchive”>
but this tag only removes the “Cached” link for the page. Google will continue to index the page and display a snippet.
To remove a page or image, you must do one of the following:
- Ensure requests for the page return an HTTP status code of either 404 or 410 OR
- Ensure that the pages you want to remove have been blocked using a robots.txt file OR
- Ensure that the pages you want to remove have been blocked using a meta noindex tag.