Every time the anonymous group targets a website, they are able to take it down.. even for large corporates / governments with professional.  I read (basic theory) about dealing with normal DDOS attack, with DDOS protection techniques.  But why do these techniques fail in case of Anonymous group attacks?  Is there any success stories about surviving through a really good organized DDOS attack?
This is a  about DoS and DDoS mitigation.   I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all 100Mbps of my available bandwidth.  Nobody can access my site because all the requests time out, and I can't even log into the server because SSH times out too!  This has happened a couple times before, and each time it's lasted a couple hours and gone away on its own.  Occasionally, my website has another distinct but related problem: my server's load average (which is usually around .25) rockets up to 20 or more and nobody can access my site just the same as the other case.  It also goes away after a few hours.  Restarting my server doesn't help; what can I do to make my site accessible again, and what is happening?  Relatedly, I found once that for a day or two, every time I started my service, it got a connection from a particular IP address and then crashed.  As soon as I started it up again, this happened again and it crashed again.  How is that similar, and what can I do about it?
I have a problem called "The Prison Problem" that I need to explain to my 9-year-old cousin. I would think that he has just started learning about divisors and perfect squares, and as such, I have a proposed solution. Any input from you guys would be welcome, as to what is the best way to go about this.  Problem:  There was a jail with 100 cells in it, all in a long row. The warden was feeling very jolly one night and told his assistant that he wanted to give all the prisoners a wonderful surprise. While they were sleeping, he wanted the assistant to unlock all the cells. This should be done, he told the assistant, by putting the key in each lock, turning it once. The assistant did this, then came back to report that the job was done. Meanwhile, however, the warden has second thoughts. "Maybe I shouldn't let all the prisoners free," he said. "Go back and leave the first cell open, but lock the second one (by putting the key in and turning it once). Then leave the third open, but lock the fourth, and continue in this way for the entire row." The assistant wasn't very surprised at this request as the warden often changed his mind. After finishing this task, the assistant returned, and again the warden had other thoughts. "Here's what I really want you to do," he said. "Go back down the row. Leave the first two cells as they are, and put your key in the third cell and turn it once. Then leave the fourth and fifth cells and turn the key in the sixth. Continue down the row this way." The assistant again did as instructed. Fortunately, the prisoners were still asleep. As a matter of fact, the assistant was getting pretty sleepy, but there was no chance for rest yet. The warden changed his mind again, and the assistant had to go back again and turn the lock in the fourth cell and in every fourth cell down the row. This continued all through the night, next turning the lock in every fifth cell, and then in every sixth, and on and on, until on the last trip, the assistant just had to turn the key in the hundredth cell. When the prisoners finally woke up, which ones could walk out of their cells?  Proposed solution:  Ten cells are left open after this process. Every cell that is a perfect square will remain open (1, 4, 9, 16, 25, 36, 49, 64, 81, and 100). If a number is not a perfect square, then it has an even number of divisors, therefore it will be "toggled" an even number of times and end up where it started (closed). Perfect squares have an odd number of divisors, so they will end up the opposite of where they started (open). How does substituting Butter for Margarine/Shortening affect the Recipe Spotlight overrides first character What's wrong: I hit CMD+SPACE to open up spotlight, typically type in the name of the application I want to start, hit enter and either the wrong app or no app at all will start, because the app name is missing the first character. "Learn to type" I hear you say but wait: as I enter the first character in the search bar, the cursor jumps to the beginning of the line and my second character input overrides the first one. So entering for example "ever", in order to start Evernote, will result in "ver". "php" to start PHPStorm will result in "hp" and start my damn HP printer app and so on.   This cursor jump to the beginning of the line will not happen in any other application and even if I accept the fact that my cursor jumps from time to time, I don't get why the second character overrides the first one. I'm not even sure if you can configure your Mac to always override the character at current position, but I surely haven't.  So this keeps on happening quite regularly and I cannot reproduce it. It just happens and when I try it again (close Spotlight, CMD+SHIFT again), it won't happen again, even if I give it like 5 tries or so.  It won't kill me but I am a software developer myself and this kind of bugs just leave me frustrated plus I can not imagine that this is the desired behavior. I have seen some talk about this issue on the internet but I did not come across a solution..  I have 3 MacBooks, different ages, all with German keyboard layouts and German set as system language and they all do this. Just mentioning this, because after that fact, I can barely imagine this isn't affecting at least a lot, if not all, MacBook (Pro?) users.   13" Pro 2010 or so 15" Pro Retina 2013 13" Pro Retina 2015   They all run El Capitan but I already encountered this before. I don't know the OS X version I had installed when I first stumbled across it. Evaluate the limit $\lim\limits_{n \to \infty} \frac{1}{1+n^2} +\frac{2}{2+n^2}+ \ldots +\frac{n}{n+n^2}$ Evaluate the limit   $$\lim_{n \to \infty} \dfrac{1}{1+n^2} +\dfrac{2}{2+n^2}+ \ldots+\dfrac{n}{n+n^2}$$   My approach :   If I divide numerator and denominator by $n^2$ I get :   $$\lim_{ n \to \infty} \dfrac{\frac{1}{n^2}}{\frac{1}{n^2} +1} +\dfrac{\frac{2}{n^2}}{\frac{2}{n^2} +1} + \ldots+ \dfrac{\frac{1}{n}}{\frac{1}{n} + 1}=0$$   but the answer is $\dfrac{1}{2}$ please suggest how to solve this.. thanks. Adding tags to files in OS X: How to use, where are tags stored, and will they work on a network? Is Switching the Neutral OK? What’s the worst that can happen if i put a switch in the neutral instead of the phase?   I just found out that 3 light bulbs sockets in my home  are connected this way, it first came to my mind to fix it but then I recalled the flow of current from positive to negative is just a convention since the electrons are charged negatively and they actually flow from N to L so i cant really find an solid excuse to mess with the wiring for the next 2 hrs How do you challenge the closing of one of your questions? As a newcomer to StackOverflow, I recently asked my first . I wanted to start with a fairly safe general question, to get the feel for how the site worked. My question was intended to be programming-related, but my original wording was not clear enough, so another user decided to close it.  I've re-phrased my question, and had received one useful answer before the question was closed, but I'm not sure what the procedure is after your question is closed to allow people to post answers again...  I've checked the FAQ and About pages, searched the SO questions, but have had no luck. Could someone point me in the right direction as to how I get my question re-opened, or if it is possible to do at all? I'm looking for ways to speed up the combat in my D&amp;D 3.5 game. It seems that turns - both player and non-player - simply take too long. I have thought about giving everyone a 30 second timer, but I'm afraid that might inhibit their ability to come up with strategy and tactics. I'm running the following script on Ubuntu 14.04:  #!/bin/bash  apt-get purge -y nginx apt-get install -y nginx  date   When I run it like cat /tmp/script | bash, apt-get starts installing, then "date" is printed (not the actual date, but the command name), then the remaining apt-get output is printed.  If however I run the script like /tmp/script, it works as expected: printing the date after apt-get finished.  Why does this happen and how can I force bash to work when being piped to the same way it does when invoked directly? Recommended shutter speed for action sports? What shutter speed do professional sports photographers typically use for action sports like football and basketball? Are there any distinct finite simple groups with the same order? In finite group theory, it's often quite easy to show that there are no simple groups of a given order $n$.  My question is different: is there some natural number $n$ such that there are two non-isomorphic simple groups of order $n$?  The two easiest families of finite simple groups - $\mathbb{Z}_p$ for $p$ a prime and $A_n$ for $n\ge5$ - clearly don't yield any examples.    It should be possible to check this using the , but I don't know enough about the fabled 'sixteen infinite families of groups of Lie type' to do the check myself.  Also, if the answer is 'no', I'd be much more interested to see an elementary(ish) proof than I would be to see a proof that relies on over 3,000 pages of non-stop hard group theory. Why does network ad URL from SO to history.SE mention Ask Ubuntu? Today, I was on Stack Overflow when I noticed an interesting ad pointing to history.SE (actual square ad, not just Hot Network Questions).  The link in the ad was:    which resolves to:  https://history.stackexchange.com/questions/23946/what-were-greek-and-roman-sails-made-from?utm_medium=ad&amp;utm_source=http-askubuntu-com-questions-471178-converting-hundreds-of-jpg-to-pdf-using-te&amp;utm_campaign=history.stackexchange.com-promo&amp;utm_content=23946  (link form for conveniece: )  The confusing part os the URL is: utm_source=http-askubuntu-com-questions-471178-converting-hundreds-of-jpg-to-pdf-using-te. The ad is from SO to history.SE, it doesn't have anything to do with Ask Ubuntu, so why does it appear in the URL? Is this a bug?  EDIT: Okay, managed to trigger it again: the page  contains this ad:    The link of the ad is:    which resolves to:  http://opensource.stackexchange.com/questions/1556/how-to-react-to-unhelpful-contributions-to-otherwise-unnoticed-projects?utm_medium=ad&amp;utm_source=http-sharepoint-stackexchange-com-questions-16925-why-am-i-getting-server-erro&amp;utm_campaign=opensource.stackexchange.com-promo&amp;utm_content=1556  incorrectly referencing an unrelated sharepoint.SE question. Setup or "set up"? The word setup (as a noun), I feel, has become an acceptable part of the English language, at least insofar as technical manuals or computer textbooks are concerned. However I find that the word is used very often in verb form like so:     "You can setup the program quite easily ..."   when in fact my understanding is that the actual sentence should be:     "You can set up the program quite easily ..."   I would like to know if setup can be used as a verb. The situation seems be very similar to the word output (as a noun). Output is a purely technical word and its use is restricted solely to technical texts or at least in a technical context within non-technical books. However it is also used in verb form now like so:     "The system will output the signal ..."   I would be very grateful if this question is answered. Thank you If $\sum_{n=1}^{\infty} a_n^{2}$ converges, then so does $\sum_{n=1}^{\infty} \frac {a_n}{n}$ So, I just finished off the first part of an important task for school and today when I was going to continue, the document with my notes were gone. The only fragment I've got left of my file is the back up file, which doesn't show in the folder where I saved the document, but I can search for it.  Is there anyway which allows me to open the back up file, save it as a text file and continue my task? I don't really have the time for running restoring tools, which never has helped me in a satisfactory way anyway.  I wrote the document in gedit and my version of Ubuntu is 12.10. I care to understand the concept behind the Borel-Cantelli Lemma better, hence I would appreciate it if someone could take the time to check if my arguments below are clear and rigorous.     Statement: Let $(X_n)_{n \geq 1}$ be a sequence of non-negative random variables that are identically distributed $X_n \sim X \geq 0 $ with $E(X)&lt; \infty$, show that $ X_n/n \to 0$ almost surely     Proof: Since $X_n \sim X$ for some non negative random variables we can easily compute that for $\epsilon &gt;0$ we have $$ \infty&gt;E(X/\epsilon) = \int_0^\infty P(X/ \epsilon &gt; t) dt = \sum_{n=1}^\infty \int_{n-1}^n P(X/ \epsilon &gt; t ) dt \geq \sum_{n=1}^{\infty} P(X/ \epsilon &gt;n) $$ Thanks to the Borel-Cantelli Lemma we obtain that $$ P ( \limsup_{n \to \infty} \lbrace X_n/n &gt; \epsilon \rbrace ) = 0 \iff P ( \liminf_{n \to \infty} \lbrace X_n/n \leq \epsilon \rbrace) = 1 $$     Question: Does the $\epsilon$ in the above depend on $k$?   I think it does and I would argue as follows $$P( \liminf_{n \to \infty} \lbrace X_n/n \leq \epsilon \rbrace )= P  \left( \bigcup_{n=0}^\infty \bigcap_{k=n}  \lbrace X_k/k \leq \epsilon (k) \rbrace \right) $$ Now using the chain of inclusions that state that we have for $\epsilon &gt;0$  $$ \lbrace \limsup |X_n-X| &lt; \epsilon \rbrace \subset \liminf \lbrace |X_n-X| &lt; \epsilon \rbrace \subset \lbrace \limsup |X_n-X| \leq \epsilon \rbrace $$ We conclude that $$ P ( \lbrace \limsup_{n \to \infty } X_n/ n \leq \epsilon(k) \rbrace)=1 $$ Where I choose the same $k \in \mathbb{N}$ as above, and then choose $k^*$ large enough such that $\epsilon(k) \leq \frac{1}{k^*}$, define the set $$ \Lambda_{k^*}:= \lbrace \limsup_{n \to \infty} X_n/n \leq 1/k^* \rbrace \implies P(\Lambda_{k^*})=1$$ and also we obtain that $\Lambda:=\bigcap_{j \geq k^*} \Lambda_{k^*}$ is still an almost sure event, i.e. $P(\Lambda)=1$ but for all realizations $\omega \in \Lambda$ we have $\limsup_{n \to \infty} X_n( \omega)/n \leq 0  \implies X_n( \omega)/n \to 0$ for all $\omega \in \Lambda$ that is$X_n/n \to 0$ almost surely $\Box$  Are my arguments given above correct and more importantly complete? Are there steps where you'd use different arguments? Plotting heat equation in a Manipulate expression Beam size and material for 15 feet long swing I need to create a 15 feet span beam for kid swing (300 lbs load / 150 lbs and 2 swings assumption). One end will bolt to the tree (just for convenience).  What "treated lumber" lumber size and material I should use? Or is it better / cheaper to use metal pipe (from the plumbing department)?  I guess 4x8x16 or two (2) 2x8x16 would do it according to this website . But I do like a clean look of metal. My wife would concern about big piece of lumber running on top of the kid (that looks heavy visually). half sine and half cosine quaternions Which is correct: I'll be moving next month or I'll be shifting next month? For changing one's home from one place to another, I've heard people in western part of the world using the sentence:      I'll be moving next month.   In India, even in the English news channels, I've heard many people using the phrase:     I'll be shifting next month.   Which one is the correct usage? Or are both of them correct and the difference in usage is regional?