I am facing a DDOS attack from a few hundred IP addresses, all of them coming from various cities in India and have the same organization: "................ for GPRS Service". (I'm not mentioning the whole name).  The attack started around 5 hours ago and it consists on hundreds of IP addresses that open 1 to 5 connections (as opposed to one or a few IPs making thousands of connections). The IP addresses are coming from a wide range of subnets.  Is there a way to tell the firewall to block the internet provider of the remote IPs, at least until the problem is solved?
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?
Hardware issue on iMac, flashing question mark I have an iMac 2008/2009 issue and recently the computer would not boot and I would get a flashing question mark. Ran through all the usual steps, try boot in safe mode, flash RAM,  try single user for fdisk, put in OS disk and boot from CD, etc... No dice.   Replaced the hard drive and put the OS disc in the system, press and hold option. (holding C didn't work) I can see the OS disk but when I click on it the system will act like it is going to run and then freeze. The best I got was the OS X disc that changed the screen to dark grey and told be the system had to restart.  Purchased a usb mount for an external hard drive. Was able to mount the old hard drive to a laptop and run disk utility. Everything checked out.  At this point I am pretty sure it isn't the hard drive.   Any other hard ware items this can point too? My iMAC can also "see" the hard drive (and the recovery partition) when connected via the USB and I hold "option" on start up. But it crashes when trying to boot from either.  I am going to take out and re-install the RAM for giggles but I am not sure what else to do.   Ideas are welcome. Sometimes, when fighting an enemy, your character will do a special move, with a third person view animation, instantly killing the enemy. But these types of moves seem to be random, sometimes being used on enemies with nearly full health, other times not having a finishing move at all during a whole fight.  What are the parameters determining when a finishing move is used? I would like to configure my Ubuntu 12.04 server to synchronize its clock with a specific NTP server. Where to set this up? Login screen loops unless you login as Guest I am running a VMWare Player with a Ubuntu 12.04 LTS Precise Pangolin as Guest on my Windows 7. Sometimes I get the shutdown blue screen error in Windows, this time it happened when I was running the Player. When I restarted everything Ubuntu gave me the &quot;Login Loop&quot; on adminstrator login. I log in and there's this black screen where I can only read:  piix4...smbus:0.0.0.07.3 Host Smbus controller not enabled .    When I go to the prompt in root mode it fails to update and only upgraded, specially some plugins ( I think graphic plugins) which also appear in one an error message after quitting the prompt, but they´are successfully installed. They are not the error message. After that I have been working with the Fail/safe Mode recovery panel. When I try to update via Root I get errors like this: W:failed to fetch http://extras.ubuntu.com/ubuntu/dists/precise/release.gpg could not        resolve 'extras/ubuntu.com  There are 8 more like this referring to areas like: -archive/canonical.com -ppa.Launchpad.net -security.Ubuntu.com -Us.archive.ubuntu.com - release.gpg                         precise-updates/release.gpg                         precise_backport/release.gpg   Final Message: some index files failed to download.....they have been ignored or old files are used. The black screens most of the time pass by too fast for me to pick up any information. But in general I think I have done everything I was able to in the recovery panel including updating network and graphic packages and recovering filesystem packages and the basic stuff ( I am a beginner regarding Linux ) in the root prompt. Now I am stuck in this screen with graphic options: - Run in low-graphics mode just for one session - Reconfigure Graphics - Troubleshoot the error - Exit to console login  I am trying to choose to reconfigure graphics but the mouse disappears in the virtual machine screen and sometimes when options change it´s only the first and last option. But this happens from the blue without messages. This particular option menu is in the regular GUI style against a black screen in Terminal style. Really strange. java.lang.OutOfMemoryError: PermGen space Exception On machine A I have the folder /home/a/  On machine B I have the folder /home/b/  I wish transfer all files, directories and sub-directories of /home/a in /home/b with sftp On machine A I tried the commands: sftp fibon82@machineB.com put /home/a/* /home/b/  but it doesn't work, i get the error message: &quot;skipping non-regular file /home/a/a1&quot;... [a1 is a sub-directory of a] How could I modify the put instruction? Thanks! :) EDIT: I solved using scp: scp -r /home/a/ fibon82@machineB.com:/home/b/ "A/An" preceding a parenthetical statement What will be a smoother transition into GNOME for Ubuntu 18.04-- Ubuntu GNOME or Vanilla Ubuntu? ^^^^ Will Ubuntu GNOME upgrade to Ubuntu 18.04, or will support discontinue when 18.04 is released?? Just want to know what's better to run right now so I can upgrade and not have to reinstall later(I intend to see this transition through)-- GNOME installed correctly on vanilla Ubuntu, or Ubuntu GNOME? Many times when going through the Close queue I see that people are using the too localized reason.  Sometimes the reason for this is in the comments (like the syntax error being pointed out), but a lot of times it's in the answer, so then I have to click on the question and look at the answers to see if it is really too localized.  Could we please get the answers shown underneath the question in the Close review queue? Pie Chart without labels in beamer using pgf-pie EDIT The accepted answer completely solves my immediate problem, but for more detailed analysis of the underlying issue please refer to answer by cfr. Basically, pstricks and pdfTex don't mix well.  I have a beamer presentation with a lot of pie charts. I use pgf-pie package because it is easy and (mostly) does what I need. I have one particular pie-chart that should have no labels at all. I have tried adding  /tikz/nodes={text opacity=0,overlay}   to the code following advice found here.    \documentclass{standalone} \usepackage{pgf-pie} \begin{document}  \begin{tikzpicture} \pie [explode=0.1, color={blue!70, green!80, red, yellow} ,/tikz /nodes={text opacity=0,overlay}]{10/, 20/, 30/, 40/} \end{tikzpicture} \end{document}   Now, the strange thing is, the code works well in the example above (standalone class). However, it doesn't seem to do anything inside a beamer presentation, i.e. the labels still show. It seems that there is some sort of package conflict. How could I enable this to work in the beamer presentation? I know there are other ways to produce this but pgf-pie is quite handy otherwise.  \documentclass[12pt,compress]{beamer} \usetheme{Warsaw}  \setbeamertemplate{navigation symbols}{}%remove navigation symbols \setbeamercolor{alerted text}{fg=magenta}  %\usepackage[latin1]{inputenc} \usepackage[T1]{fontenc} \usepackage{wasysym} \usepackage{multicol} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{xcolor} %\usepackage{iwona} \usepackage{wrapfig} \input{FactorTree} \usepackage{pstricks} \usetikzlibrary{matrix} \usepackage{tkz-euclide} \usetkzobj[all] \usepackage{xlop} \usepackage{tcolorbox} \usepackage{pgfplots} \usepackage{pgf-pie} \usepackage[makeroom]{cancel} \input{longdiv} If I pass PHP variables with . in their names via $_GET PHP auto-replaces them with _ characters. For example:  &lt;?php echo "url is ".$_SERVER['REQUEST_URI']."&lt;p&gt;"; echo "x.y is ".$_GET['x.y'].".&lt;p&gt;"; echo "x_y is ".$_GET['x_y'].".&lt;p&gt;";   ... outputs the following:  url is /SpShipTool/php/testGetUrl.php?x.y=a.b x.y is . x_y is a.b.   ... my question is this: is there any way I can get this to stop? Cannot for the life of me figure out what I've done to deserve this  PHP version I'm running with is 5.2.4-2ubuntu5.3. The force of gravity is constantly being applied to an orbiting object.  And therefore the object is constantly accelerating.  Why doesn't gravity eventually "win" over the object's momentum, like a force such as friction eventually slows down a car that runs out of gas?  I understand (I think) how relativity explains it, but how does Newtonian mechanics explain it? My csv export displaying html, how to get rid of? Positrons versus holes as positive charge carriers : [The Dirac sea is a theoretical model of the vacuum as an infinite sea of particles with negative energy. It was first postulated by the British physicist Paul Dirac in 1930 to explain the anomalous negative-energy quantum states predicted by the Dirac equation for relativistic electrons. The positron, the antimatter counterpart of the electron, was originally conceived of as a hole in the Dirac sea, well before its experimental discovery in 1932.]  and:  [Dirac's idea is completely correct in the context of solid state physics, where the valence band in a solid can be regarded as a "sea" of electrons. Holes in this sea indeed occur, and are extremely important for understanding the effects of semiconductors, though they are never referred to as "positrons". Unlike in particle physics, there is an underlying positive charge — the charge of the ionic lattice — that cancels out the electric charge of the sea.]  It always confused me to think of holes as positive charge carriers in semi-conductors as not being real: real electrons move from one lattice-position to another lattice-position, which effectively looks like a positive hole in the lattice that is moving in the other direction, but in reality a real electron moves, the hole is kind of an "illusion".  On the other hand the positrons are always introduced as real hard-core particles.   The quotes from the Wikipedia article make me unsure: how should I look upon these phenomena?   Edit: holes in a Dirac sea give rise to real pos. entities in one case and to unreal pos. entities in another - how can we distinguish, is it a matter of formalism? When I apply a glossy shader to the material of my text, the text becomes just black. Why?    I have lamp and everything, but the problem persists. The text is red before I add the glossy shader.  I'm using Cycles render.   Thanks! Has anyone used PostgreSQL with PostGIS successfully?   I am a semi-experienced ArcGIS user and want to build out a database and connect it to ArcCatalog.   I've scoured the internet for resources but nobody has really given a good walkthrough. I am trying to find the largest file in a directory recursively. If there is a subdirectory inside of that directory the function needs to go inside that directory and check to see if the largest file is there. Once the largest file is found the output is displayed with the relative path name and the name and size of the largest file.  EX:  dude@shell2 (~...assignment/solutions) % bash maxfile.sh ~/test class/asn dude.h.gch: 9481628   This is what I have:  #!/bin/sh clear  recursiveS() {     for d in *; do         if [ -d $d ]; then             (cd $d; echo $(pwd)/$line; du -a; recursiveS;)         fi     done } recursiveS   I have been stuck for a while now. I cannot implement this by pipelining a number of existing Unix tools. Any ideas would be nice! Effect of each parameter on a Monte Carlo Simulation I was wondering what is the best way to determine the effect of each random parameter on the result obtained from a Monte Carlo Simulation.  I realise I have asked a similar question , but this time I am making this question in a more general manner as I didn't get any answers previously.   Background: I'm essentially running a Monte Carlo Simulation where I sample randomly from 65 Normal Distributions and 2 Uniform Distributions. Then, i then input these values to a linear equation and run this for 500.000 iterations. I just wanted to determine the best way to establish the relative effect of each of these 67 (in total) random variables on the final outcome from my Monte Carlo Simulation. In transformers, the ratio of the voltages equals the ratio of the turns - so double the output coil's turns and the output voltage doubles. Then, in order to conserve energy, current halves.  This makes perfect sense in terms of $\mathrm{P=VI}$, but what happened to $\mathrm{V=IR}$? Doubling voltage and halving the current seems to completely contradict this basic law. That is, of course, unless the resistance in the output circuit changes, with R proportional to $\mathrm{V^2}$ - but I don't see how this is possible.  So how can a transformer obey both laws? Can resistance change or am I missing something else? Android does not download any files from untrusted CA certificate site