I have a disturbing problem for a few weeks now ... One of my three DNS-servers (running bind9 as slave of a Plesk DNS master) is getting spammed with senseless DNS requests. The origin IPs of those requests are from all over the world, so I can't just drop an IP range or a whole country by iptables.  Here are a few log lines so you can see the scheme of those "attacks":  10-May-2015 11:15:54.714 client 120.87.202.161#47441: query: sjgzincrmxobabst.www.luzhiye.com IN A + (my-ip) 10-May-2015 11:15:56.252 client 111.187.196.51#41387: query: mrcf.www.330dp.com IN A + (my-ip) 10-May-2015 11:15:56.806 client 89.90.44.173#56673: query: qzwp.www.330dp.com IN A + (my-ip) 10-May-2015 11:15:57.891 client 116.93.242.237#55721: query: srapafupglkxaver.www.330dp.com IN A + (my-ip) 10-May-2015 11:15:59.611 client 123.153.92.59#20847: query: yj.www.330dp.com IN A + (my-ip)   Those requests are not really attacks because the host server is very relaxed. I tried to block the requests with iptables, but after a few minutes/hours the requested domains are changing, so I have no chance to do so.  Chain INPUT (policy ACCEPT) target     prot opt source               destination DROP       all  --  anywhere             anywhere             STRING match  "888fy.com" ALGO name bm TO 65535 DROP       all  --  anywhere             anywhere             STRING match  "taohua.me" ALGO name bm TO 65535 DROP       all  --  anywhere             anywhere             STRING match  "yymo.us" ALGO name bm TO 65535 DROP       all  --  anywhere             anywhere             STRING match  "taohuazu.cc" ALGO name bm TO 65535 DROP       all  --  anywhere             anywhere             STRING match  "taohua.me" ALGO name bm TO 65535 DROP       all  --  anywhere             anywhere             STRING match  "227x.com" ALGO name bm TO 65535   Does anyone have experience with these kind of "attack"? How to stop it? I tried to shutdown the whole server for 48 hours. After the restart there were no attacks anymore, but a few hours later they started again.  Configuration (named.conf.local / named.conf.options):  dnssec-validation auto; allow-new-zones yes; notify master-only;  auth-nxdomain no;    # conform to RFC1035 listen-on-v6 { any; };  statistics-file "/var/cache/bind/named.stats"; zone-statistics yes;  controls {         inet * port 953 allow { plesk-ip; 127.0.0.1; } keys {"rndc-key"; }; };  logging {         channel b_query {                 file "/var/log/bind9/query.log" versions 2 size 1m;                 print-time yes;                 severity info;         };         category queries { b_query; }; };   I ran a few online tests to verify again that my DNS server is not an open resolver. Successfully: No open resolver found.  Help is really appreciated!
This is a  about securing public DNS resolvers   Open DNS servers seem pretty neat and convenient, as they provide IP addresses that we can use consistently across our company regardless of where they are located. Google and OpenDNS provide this functionality, but I'm not sure that I want these companies to have access to our DNS queries.  I want to set up something like this for use by our company, but I hear a lot about this being dangerous practice (particularly in regards to ) and I want to make sure that we do this right. What things do I need to keep in mind when building this type of environment?
Prove that T is diagonalizable if and only if the minimal polynomial of T has no repeated roots. Oven Temperature: How to be sure the selected temperature is correct. I suspect that my - fairly new - oven gets too hot, so I bought an oven thermometer, which confirmed this.  So I called the supplier.  They say that in order to obtain the correct actual  oven temperature, for any setting, you take the highest reading on the thermometer, and the lowest, and then divide both readings.   Is this correct? Listing, zebra effect and broken lines In , I've found one solution to produce a zebra effect for listing. Unfortunately, this only works if the lines are not broken. Is there a way to fix this?  Here is a code with an example showing the problem:  \documentclass[10pt,a4paper]{article}     \usepackage[utf8x]{inputenc}     \usepackage{ucs}     \usepackage[T1]{fontenc}     \usepackage{lmodern}     \usepackage[frenchb]{babel}     \usepackage[x11names, svgnames]{xcolor}     \usepackage{graphicx}     \usepackage{listings}     \usepackage{amsfonts}     \usepackage{amssymb}      \makeatletter         % Patch line number key to call line background macro         \lst@Key{numbers}{none}{%             \def\lst@PlaceNumber{\lst@linebgrd}%             \lstKV@SwitchCases{#1}%             {none&amp;\\%              left&amp;\def\lst@PlaceNumber{\llap{\normalfont                         \lst@numberstyle{\thelstnumber}\kern\lst@numbersep}\lst@linebgrd}\\%              right&amp;\def\lst@PlaceNumber{\rlap{\normalfont                         \kern\linewidth \kern\lst@numbersep                         \lst@numberstyle{\thelstnumber}}\lst@linebgrd}%             }{\PackageError{Listings}{Numbers #1 unknown}\@ehc}}          % New keys         \lst@Key{linebackgroundcolor}{}{%             \def\lst@linebgrdcolor{#1}%         }         \lst@Key{linebackgroundsep}{0pt}{%             \def\lst@linebgrdsep{#1}%         }         \lst@Key{linebackgroundwidth}{\linewidth}{%             \def\lst@linebgrdwidth{#1}%         }         \lst@Key{linebackgroundheight}{\ht\strutbox}{%             \def\lst@linebgrdheight{#1}%         }         \lst@Key{linebackgrounddepth}{\dp\strutbox}{%             \def\lst@linebgrddepth{#1}%         }         \lst@Key{linebackgroundcmd}{\color@block}{%             \def\lst@linebgrdcmd{#1}%         }           % Line Background macro         \newcommand{\lst@linebgrd}{%             \ifx\lst@linebgrdcolor\empty\else             \rlap{%                 \lst@basicstyle                 \color{-.}% By default use the opposite (`-`) of the current color (`.`) as background                 \lst@linebgrdcolor{%                 \kern-\dimexpr\lst@linebgrdsep\relax%                 \lst@linebgrdcmd{\lst@linebgrdwidth}{\lst@linebgrdheight}{\lst@linebgrddepth}%                 }%             }%             \fi         }     \makeatother      \lstset{ %    * Number for lines         numbers=left,                   % Where to put the line-numbers         numberstyle=\footnotesize,      % Size of the fonts used for the line-numbers         stepnumber=1,                   % Step between two numbers         numbersep=5pt,                  % How far the line-numbers are from the code % %    * Back returns for long lines         breaklines=true,                % Sets automatic line breaking         breakatwhitespace=false,        % Automatic breaks only happen at whitespace ?         breakindent=0pt,                % Space before the text of a break         postbreak=\mbox{                % Character used at the begining of a break             \rotatebox[y=0.9ex]{180}{\color{Red} $\Lsh$}%         },     }  \begin{document}  \begin{lstlisting}[language=Python,linebackgroundcolor={\ifodd\value{lstnumber}\color{gray}\fi}] for i in range(5): for i in range(5): for i in range(5): for i in range(5): for i in range(5): for i in range(5):     sum += i**3 print sum  print('Fin de la boucle...') \end{lstlisting}  \end{document} Why haven't I received the "Curious" badge? As you can see in the picture, I have 13 out of 5. But it's been like this for about two months! What's the reason for that? SQL Server Escape an Underscore How do I escape the underscore character?  I am writing something like the following where clause and want to be able to find actual entries with _d at the end.  Where Username Like '%_d' Regular Expression Uppercase Replacement in C# I have the following C# which simply replaces parts of the input string that look like EQUIP:19d005 into URLs, like this:  input = Regex.Replace(input, @"(EQUIP:)(\S+)", @"&lt;a title=""View equipment item $2"" href=""/EquipmentDisplay.asp?eqnum=$2""&gt;$1$2&lt;/a&gt;", RegexOptions.IgnoreCase);   The HTML ends up looking like this.  &lt;a title="View equipment item 19d005" href="/EquipmentDisplay.asp?eqnum=19d005"&gt;EQUIP:19d005&lt;/a&gt;   The only trouble is that the destination page expects the eqnum querystring to be all UPPERCASE so it returns the correct equipment when eqnum=19D005 but fails if it receives eqnum=19d005.  I guess I can modify and correct EquipmentDisplay.asp's errant requirement of uppercase values however, if possible I'd like to make the C# code comply with the existing classic ASP page by uppercasing the $2 in the Regex.Replace statement above.  Ideally, I'd like the HTML returned to look like this:  &lt;a title="View equipment item 19d005" href="/EquipmentDisplay.asp?eqnum=19D005"&gt;EQUIP:19d005&lt;/a&gt;   Notice although the original string was EQUIP:19d005 (lowercase), only the eqnum= value is uppercased.  Can it be done and if so, what's the tidiest way to do it? Obtaining a formula for prediction limits in a linear model (i.e.: prediction intervals) Let's take the following example:  set.seed(342) x1 &lt;- runif(100) x2 &lt;- runif(100) y &lt;- x1+x2 + 2*x1*x2 + rnorm(100) fit &lt;- lm(y~x1*x2)   This creates a model of y based on x1 and x2, using a OLS regression.  If we wish to predict y for a given x_vec we could simply use the formula we get from the summary(fit).  However, what if we want to predict the lower and upper predictions of y? (for a given confidence level).  How then would we build the formula? Show that there is $\xi$ s.t. $f(\xi)=f\left(\xi+\frac{1}{n}\right)$ Let $f:[0,1]\to\mathbb{R}$ be continuous and $f(0)=f(1)$. Show that for any integer $n\geqslant 2$, there is $\xi\in(0,1)$ s.t.$f(\xi)=f\left(\xi+\frac{1}{n}\right).$  I think this requires the intermediate value theorem somewhere. (Re?)Install Ubuntu on a Dell laptop that had Ubuntu preinstalled I have a complex integral $$\int_{|z|=r}x \, dz$$ for the positive portion of the circle.  I know that this integral seems easy enough but I am having trouble with it, and I'm fairly certain my answer is incorrect.  I wanted to use a parameter such that $x=r\cos\theta$, so we then have $dz=dx+i\,dy=dx$ since there is no reason to have have the $i\,dy$ since the imaginary part is equal to $0$.  So now I have the double integral  $$\int^r_0\int^\pi_0 r \cos\theta \, dx$$  which equals $0$ since integration the $\cos\theta$ gives $\sin\theta$ and evaluated from $0$ to $\pi$ makes the integral evaluate to $0$.  Am i misinterpreting part of the question?  Way off base?  The book suggests to also solve the problem by realizing $x=\frac{1}{2}\left(z+\frac{r^2}{z}\right)$ along the circle.  For this portion of the problem I assume that I would integrate the above by $z$ as if it were a normal calculus problem, but I have problems with what to put as upper and lower limits.  Thanks in advance! Let $G$ be a locally compact Hausdorff Abelian topological group.  Let $\mu$ be a Haar measure on $G$, i.e. a regular translation invariant measure.  Let $f$ be fixed in $\mathcal{L}^1(G, \mu)$.  Define the function from $G$ to $\mathcal{L}^1(G)$ that assigns to each $y$ in $G$ the function that takes $x$ in $G$ to $f(xy^{-1})$.  I.e. it assigns the $y$-translate of $f$.  Is this a continuous function of $y$ into $\mathcal{L}^1$?      On p.94 3.10 of  it is asserted that it is.  The usual proof of this sort of thing in cases where $G=\mathbb{R}$, say, is you use density of compactly supported continuous functions, and then dominated convergence.  The former survives, but dominated convergence does not work on nets.  In fact, a limit of a net of measurable functions need not be measurable. I have a client that has a Links page in SharePoint 2013. On the page is a column called URL that is set as a hyperlink column, but they want the column to accept pw://example.com/... instead of just ...  Is there a way to change the hyperlink column to allow for this behavior? I considered creating it as a single line of text and then making that text box a hyperlink-enabled box. Is there another native option? If not, which of these would be easiest? I am new to SharePoint so any help would be appreciated! Thanks in advance!   URL    Type the Web address: (Click here to test)  pw://test  Invalid URL: pw://test Meta duplicates don't require an answer. Don't suggest there is one when that's not true In how many ways $5$ different rings can be worn on $4$ fingers ?   Although these is similar question here   But I want to answer it in different way which is like take $4$ fingers like $a,b,c,d$. Now $a$ can be filled in $5$ ways and so are others. So total ways are $5^4$ but answer is $4^5$. What is wrong in my reasoning? Which cases have I left out? Smart Phone's camera socket I just want ask how the socket in the image is called?   I couldn't really find and the closer I could get is only Raspberry's module. Converting a Java Keystore into PEM Format I am trying to convert from a Java keystore file into a PEM file using keytool and openssl applicactions. But I could not find a good way to do the conversion. Any ideas?   Instead of converting the keystore directly into PEM I tried to create a PKCS12 file first and then convert into relevant PEM file and Keystore. But I could not establish a connection using them. (Note that I just need a PEM file and a Keystore file to implement a secured connection. There is no restriction like "Start from a java keystore file". :) So starting from other formats is acceptable with my case)  But a direct conversion method from jks to pem is preferable. What does the symbol with a shield and two swords next to clan members' names mean? When I open my clan roster, I now notice there is a symbol that has a shield + two swords next to most clan member's name.  What does this signify?  Are they ready for clan battles? Return FileName Only when using OpenFileDialog I want to make someone a present by subscribing for him to a mathematical journal. (It should appear every month or every two months). The contents should be comprehensible to an undergraduate in mathematics, and be about a broad selection of topics (for example not only analysis).   I expect the content to be something like proposing interesting problems and then giving solutions with some references for further study. Are there some famous journals you could suggest me? Transformer VA Ratings, Power factor, and Pulsed current What exactly goes into a transformer's VA rating? At a fundamental level it seems that there has to be a limit to what the VA rating can represent.  For example if I draw 2 Amps-RMS from the secondary of a 30VA rated transformer at 15 Vrms this makes sense as the maximum Complex Power I can draw. Still, at a power factor of 1 my maximum current in the transformer would be sqrt(2) * 2 Amps.   But what if my power factor is abysmally low (ie in a DC rectifier) due to harmonic distortion and while I still draw 2A-RMS I have brief current spikes of 15 Amps? Surely the transformer's magnetics couldn't handle these spikes as I'd expect the core would saturate.  My question is what is the practical limit for VA ratings of transformers? Would brief current spikes that reduce to only 2A-RMS in this case be fine? Obviously the secondary/primary copper losses play a part in the rating but how do the magnetics factor in?  I ask this because I am designing a simple bench power supply using a 125VA transformer with a 24Vrms secondary and am trying to figure out how much power I can draw before the current spikes into the inductor are too much for the transformer. I also don't want to have to resort to active PFC as I don't want to risk messing up any HVAC PCB design.  Thank you