Temporary file security threat? We use CentOS.  We've been hacked and trying to figure out why. Looking at the /tmp folder I'm wondering if these are security threats:  -rw-rw----  1 mysql    mysql    11665408 Apr  3 18:59 #sql_6bc_0.MYD -rw-rw----  1 mysql    mysql        1024 Apr  3 18:59 #sql_6bc_0.MYI drwxrwxrwt  5 root     root       647168 Apr  3 18:59 ./ dr-xr-xr-x 25 root     root         4096 Mar 31 19:34 ../ drwxrwxrwt  2 root     root         4096 Mar 31 19:34 .ICE-unix/ -rw-------  1 cpanel   cpanel          0 Dec  3 11:18 .ftpquota -rw-------  1 root     root            1 Mar 18 00:19 cache_03ccc987bb84ad942c7bdc1b37a1d5af -rw-------  1 root     root            1 Mar 18 00:19 cache_0f1ff313f7d5dc65958843d70148d9f6 -rw-------  1 root     root            1 Mar 18 00:19 cache_3ebbab63ff1d3bffdaddb17747049f2d -rw-------  1 root     root          581 Mar 14 00:46 cache_5a3dafb5b1cf70a9b76b7e70107b3ba0 -rw-------  1 root     root            1 Mar 18 00:19 cache_763860a21a94412ffb8081c5efb43196 -rw-------  1 root     root            1 Mar 18 00:19 cache_85daced7c4de2f5a2c332a7d8a7a3803 -rw-------  1 root     root            1 Mar 18 00:19 cache_8c1e2d0573ed1f99fd247768110f872f -rw-------  1 root     root        16093 Mar 18 00:19 cache_b9813b3134c6afdd77d72c595ebda25d -rw-------  1 root     root          440 Mar 18 00:19 horde_cache_gc -rwxr-xr-x  1 root     root        34087 May 16  2013 latest* lrwxrwxrwx  1 root     root           27 Dec  3 11:15 mysql.sock -&gt; ../var/lib/mysql/mysql.sock= drwxr-xr-x  3 root     root         4096 Dec  3 11:31 pear/ -rw-------  1 user user   122856 Mar 31 00:13 php9YFHLD -rw-------  1 user user           0 Apr  3 18:38 sess_00257f10fae6be00b90d5ba805ad30af -rw-------  1 user user           0 Apr  3 18:58 sess_003d98e029b3d2c0fab09d926c0dd761 -rw-------  1 user user           0 Apr  3 18:59 sess_0047577f2d01487f4fa75724d0b3f7ee -rw-------  1 user user           0 Apr  3 18:58 sess_0070e5da229b113786f64f39cae87daf -rw-------  1 user user           0 Apr  3 18:59 sess_0077dea73523b2548e8eb100ff76359f -rw-------  1 user user           0 Apr  3 18:46 sess_00882cd396bd3452665c9d973918afdb -rw-------  1 user user           0 Apr  3 18:46 sess_00b82f19cf9a685d1aceeb7f70de6608 -rw-------  1 user user           0 Apr  3 18:50 sess_00d77c2027af0c19151a1b99021f3758 -rw-------  1 user user           0 Apr  3 18:51 sess_0108c3a1bd1f79e0aa0b27045e23ea08 -rw-------  1 user user           0 Apr  3 18:53 sess_011637bd373ae7cffb2725820d89fd5a -rw-------  1 user user           0 Apr  3 18:43 sess_0131292a1d637c2317dcaafed09df456   Was wondering why so many of them are run by root? Why are some of them still there after so many days?  I heard about tmp files being a vulnerability. How should I monitor the /tmp files?
How do I deal with a compromised server? This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.
JUnit @Test expected annotation not working For a finite set $S$ there are $\vert S\vert!$ orderings of its elements.  What is the cardinality of all orderings of $\mathbb{N}$?  What would $$\vert \mathbb{N}\vert!$$ mean?  Is it $\prod_{n\in\mathbb{N}} \aleph_0=\aleph_0^{\aleph_0}=\aleph_1$?   says the "equivalence classes of well-orderings of the natural numbers" has cardinality $\aleph_1$.  But I can't put together in my mind the connection between well-orderings of $\mathbb{N}$ and all orderings of $\mathbb{N}$.  (Are there non well-ordered orderings of $\mathbb{N}$?)  This leads to wondering what the cardinality of all orderings of $\mathbb{R}$ is.  (Actually my thought process went in the other direction, from $\mathbb{R}$ to $\mathbb{N}$.)  I think knowing the answer to the above question will teach how to determine what $$\vert \mathbb{R}\vert !$$ means, if anything.  I will be happy if you assume the continuum hypothesis to be true for the purposes of this question, but any level of completeness is welcome. The vertical line at the end of the cell where i used cell merge is missing. Using (or not) the word "to" in a sentence ending with "be able" How did "sinister", the Latin word for "left-handed", get its current meaning? Sinister is the Latin word for left-handed.  What evolution of meaning turned left-handed into evil and threatening? Random piece of plastic I have recently purchased a hybrid bike with suspension (not sure if that is relevant to this question). It came with two pieces of plastic. Any ideas what they may be for? Saving for retirement without employer sponsored plan I'm considering moving to a new job that doesn't have any sponsored retirement plans.  I'd like to continue saving on my own though, but it seems that IRAs have a $5,000 contribution limits.  What are some other options to save in addition to an IRA?  I'm not interested in the obvious "put more into your bank savings account," I'm looking for options fairly close to an IRA (trading stocks on etrade also out) to save more.  Also, would contributions to the 401k prior to rolling into an IRA count against the contribution limit to the IRA? How do I disable fog on specific camera/s Dryer Outlet - 4 prong to 3 prong Our new dryer has 3 prongs vs. 4. We are changing to the new 3 prong dryer outlet, but want to make sure we are grounding. The wires coming from the wall our white, red &amp; black - the the copper wire. Do I need to ground it?? Thank you! Molly The usual explanation for warm fluids rising past cooler ones is that the warmer fluid has a lower density.  I'm trying to understand what this looks like at a molecular scale.  The density seems to be a large-scale phenomenon, and I don't understand how it can affect whether a particular molecule rises or falls.  Consider a cylinder of fluid that is being heated at the bottom.  The molecules at the bottom have a higher average energy.  How does this result in the tendency of the warmer molecules at the bottom to move upwards past the cooler ones? So, we know that there is no "natural" isomorphism between a finite dimensional vector space $X$ and its dual $X^{\vee}$. However, given a basis for $X$ $(e_1, \dots, e_n)$ we can always construct a (dual) basis $(e^1, \dots, e^n)$ for $X^{\vee}$ that satisfies $e^i(e_j) = \delta^i_j$. It follows that $V \approx V^{\vee}$ simply because they have the same finite dimension $n$. Now, it seems to me that we can construct an isomorphism by assigning $$ e_i \mapsto e^i $$ and extending by linearity. That is, for an arbitrary vector $v \in X$ given by $v = \sum v^ie_i$ we can specify a linear map   $$\phi:V \rightarrow V^{\vee}$$  by  $$ \phi(\sum v^ie_i) := \sum v^ie^i $$ It is a quick exercise to check that $\phi$ is an isomorphism. Now, although this construction seems correct, there is something that doesn't quite sit right with me about it. For one thing, there is no way to really make sense of the summation convention as the right side of the function will always contain two superscripts thus requiring an explicit summation sign. The other thing that feels rather off is actually taking a lower index and moving it to an upper index, i.e., $e_i \mapsto e^i$ (which, of course, is the reason that the summation convention doesn't work).  So, with this background my questions are   Is there any sense in which the above isomorphism is "favored" or "canonical"? Is there another way to construct an isomorphism between a vector space and its dual, that would "conserve indexes", for lack of a better way to state it. My guess here is that the answer is no but becomes possible if one assumes $V$ has an inner product. htl5 voice recording with isualization R version 3.1.1 (2014-07-10) -- "Sock it to Me" &gt; bl &lt;- c(140, 138, 150, 148, 135) &gt; fu &lt;- c(138, 136, 148, 146, 133) &gt; t.test(fu, bl, alternative = "two.sided", paired = TRUE) Error in t.test.default(fu, bl, alternative = "two.sided", paired = TRUE) :  data are essentially constant   Then I change just a single character in my fu dataset:  &gt; fu &lt;- c(138, 136, 148, 146, 132)   and it runs...  &gt; t.test(fu, bl, alternative = "two.sided", paired = TRUE)      Paired t-test   What am I missing here? How do you Xforward windows using ssh? I have 2 graphics cards (Tesla k10, K40) in my supermicro SuperServer (7047GR-TPRF). I installed Ubuntu Server 14.04, but when I install cuda or Nvidia graphics driver (version 311 or 340), my Ubuntu desktop hangs on login. What is the Stack Exchange (Staff) process of launching a site? Inner join using an array column Having trouble indexing and executing a query in O (log n) time.  The query includes an INNER JOIN, an ORDER BY, and an equality operation. If I understand the laws of databases correctly, a query can be indexed and executed in O (log n) time (or thereabouts) if a non-equality operator is not used on more than one column. In this case, I believe the INNER JOIN does count as an equality operator and the non-equality operator would be the ORDER BY portion of the query. This table has upwards of 10,000,000 rows and needs to handle several reads and writes per second.  Using PostgreSQL. This is what the table looks like. As you can see, the column 'Names' is a list property and it is the column that the INNER JOIN goes against:  Age Names                       Date 34  ['carla', 'john', 'sam']    3/13/2011 26  ['json', 'cindy', 'joel']   3/13/2011 72  ['beth', 'amber', 'susie']  3/13/2011 14  ['john', 'jim', 'debie']    3/13/2011   This is the query that we are trying to do:  SELECT * FROM the_table WHERE Age==26 AND Names=='john' ORDER BY Date   My background is from using App Engine's Big Table, so I've used equality operators here to indicate that 'john' should be one of the names in the Names column. This would be an acceptable query in GAE's big table, it would execute in O (log N) time as all Big Table queries are reqyured to do. I am assuming there is a way to do this in PostgreSQL as well since PostgreSQL accepts list data types as columns.  Is this possible to do in PostgreSQL?  If so, how should the index be set up (we can't figure out how to set up an index that takes into account the three properties)? How to have two versions of PHP installed and switch easily between them? I want to have both PHP 5.2.17 and PHP 5.3.5 installed on my Ubuntu machine and switch as per my necessity. How can I achieve this? VAR or VECM for a mix of stationary and nonstationary variables I have 4 time series. One of them is stationary and rest of them are not. I need to find relation between them. I will use AIC to decide lag length.   Should I use VAR or VECM to find relation between them?  Will VAR or VECM give me relation in terms of equation which can be used for forecasting?  Do I need to perform Johansen's test of cointegration?  What good would it do? What does the , operator do in C?