Artur, On 11/30/2016 10:41 AM, Jaaz Portal wrote: > no it looks like dos, its dos > > i told you they dosed before bind server until we changed it to other > vendor, > and later was scanning my host for apache vulnerabilities > > configuration is standard, the only thing i changed (after your guidance) > is connection_timeout > but this does not work for this exploit > > workers.properties > worker.list=ajp13_worker > > # > #------ ajp13_worker WORKER DEFINITION ------------------------------ > #--------------------------------------------------------------------- > # > > # > # Defining a worker named ajp13_worker and of type ajp13 > # Note that the name and the type do not have to match. > # > worker.ajp13_worker.port=8009 > worker.ajp13_worker.host=localhost > worker.ajp13_worker.socket_timeout=60000 > worker.ajp13_worker.type=ajp13 > # > # Specifies the load balance factor when used with > # a load balancing worker. > # Note: > # ----> lbfactor must be > 0 > # ----> Low lbfactor means less work done by the worker. > worker.ajp13_worker.lbfactor=1 > > # > # Specify the size of the open connection cache. > #worker.ajp13_worker.cachesize > > # > #------ DEFAULT LOAD BALANCER WORKER DEFINITION ---------------------- > #--------------------------------------------------------------------- > # > > # > # The loadbalancer (type lb) workers perform wighted round-robin > # load balancing with sticky sessions. > # Note: > # ----> If a worker dies, the load balancer will check its state > # once in a while. Until then all work is redirected to peer > # workers. > worker.loadbalancer.type=lb > worker.loadbalancer.balance_workers=ajp13_worker > > ------------ > server.xml > > > <Connector port="8009" protocol="AJP/1.3" connectionTimeout="60000" > redirectPort="8443" maxConnections="256" keepAliveTimeout="30000"/> > > best, > artur
From the following fine documentation (which André has posted before): http://tomcat.apache.org/connectors-doc/reference/workers.html connection_pool_timeout (lots of stuff) . . . last paragraph: You should keep this time interval in sync with the keepAliveTimeout attribute (if it is set explicitly) or connectionTimeout attribute of your AJP connector in Tomcat's server.xml. Note however, that the value for mod_jk is given in seconds, the one in server.xml has to use milliseconds. The last line of the above snippet of the documentation is very important. Now let's look at your values. From workers.properties: worker.ajp13_worker.socket_timeout=60000 From server.xml connectionTimeout="60000" So your socket_timeout value from workers.properties is 60,000 seconds (16 hours, 40 minutes), while your connectionTimeout value is 60,000 milliseconds (1 minute). And your keepAliveTimeout (30,000 = 30 seconds) is not in sync with either value. So . . . 1. remove keepAliveTimeout from your AJP connector 2. change worker.ajp13_worker.socket_timeout to 60 This will at least get you in line with the documentation. You can then proceed to diagnose whether you have a DOS (or DDOS) attack, an application issue, or if this solved the problem. . . . just my two cents (if I've done the math right) /mde/ > > 2016-11-30 19:21 GMT+01:00 Mark Eggers <its_toas...@yahoo.com.invalid>: > >> Artur, >> On 11/30/2016 8:36 AM, Jaaz Portal wrote: >>> hi, >>> they has tried again with success despite setting connection_timeout and >>> limiting number of clients by mod_bw >>> the tomcat has frozen again. >>> >>> netstat does not showed any connections on port 80 but plenty of >>> connections from apache to localhost:8009 >>> so it was not an attack that you has described (no slowlaris) >>> >>> im looking into debug files of mod_jk and forensic for some hints. If you >>> want i can share them (they have 4mb compressed) >>> >>> best wishes >>> artur >> >> This is beginning to look like an application or a configuration issue >> and not a DOS (or DDOS) attack. >> >> One the issues that may cause this is a mismatched timeout value between >> connection_pool_timeout in workers.properties (mod_jk) and the >> connectionTimeout in server.xml (Tomcat) for the AJP connector. >> >> Also, at least for the mod_jk version that I'm running, there is no >> limit for reply_timeout (mod_jk) by default. >> >> Can you post your workers.properties file and the AJP connector portion >> of your server.xml? >> >> In the conf directory of the mod_jk source code, there is a very nice >> workers.properties file that has sensible defaults. If you've not done >> so, I suggest that you start with the values specified in that file, and >> make sure that the timeout values match (see my comment above). >> >> Also, when you used mod-proxy, did you use mod-proxy-ajp or >> mod-proxy-http? If you used mod-proxy-ajp, then again there could be a >> timeout mismatch (or no timeout specified at all). >> >> . . . just my two cents >> /mde/ >> >>> >>> 2016-11-29 11:01 GMT+01:00 André Warnier (tomcat) <a...@ice-sa.com>: >>> >>>> On 28.11.2016 22:04, Jaaz Portal wrote: >>>> >>>>> hi Andre, >>>>> you are wrong. This vulnerability is not only causing memory leaks, it >>>>> makes also apache workers to hang >>>>> >>>> >>>> Maybe for the last time here : >>>> >>>> - what do you call "apache workers" ? >>>> >>>> , making it easy to exhaust the pool. >>>> >>>> - what do you call "the pool" ? >>>> >>>> what i have in my log files. But it is true also that such exhaustion >> can >>>>> be made by other forms of dos attacks described in this thread. >>>>> >>>>> regarding you suggestion on our application, it does not dos bind >> server >>>>> nether does not scan for various vulnerabilities in apache, what i have >>>>> also in the logs >>>>> >>>> >>>> For your information : I run about 25 Internet-facing Apache webservers >>>> (some with a back-end tomcat, some not). >>>> On every single one of those webservers, there are *hundreds* of such >>>> "scans" every day, as shown by the Apache access logs. That is just a >> fact >>>> of life on the Internet. >>>> They are annoying, but most of them are harmless (from an "attack" point >>>> of view), because they are scanning for things that we do not run >>>> (phpmyadmin, xmlrpc, vti_bin, etc., etc., the list is almost endless), >> and >>>> thus are responded to by Apache as "404 Not found". >>>> What is annoying with those scans, is >>>> a) that they fill the logfile, and thus make it more difficult to find >>>> really significant things >>>> b) that each of those requires some bandwidth and system resource, if >> only >>>> to return a "404 Not found" (or a "401 Unauthorised"), and that we pay >> for >>>> that bandwidth and resources. >>>> >>>> If I could find a way to charge 0.1 cent per access to my servers, from >>>> the people who wrote or run the programs who are doing this, I could >> retire >>>> in luxury. >>>> >>>> But they are not a real problem, because they are caught as "invalid" by >>>> Apache, and rejected quickly, so they cannot do anything really nasty >>>> (except if they were sending several thousand such requests per second >> to >>>> one of my servers for a long time). >>>> >>>> The ones that are worrying, are the ones >>>> - a) which do /not/ end up as a "404 Not found", because they have found >>>> an application which responds, and they are not coming from our >> legitimate >>>> customers >>>> - b) /the ones which we do not see/, because they either do not send a >>>> valid HTTP request, or they have found a way to trigger one of our >>>> applications, in such a way that the application misbehaves and, >> perhaps, >>>> even if they do not crash our servers, they may provide the attacker >> with >>>> some entry point to do other things which we do not know and do not >> control >>>> >>>> What I am trying to say here, is /do not jump to premature conclusions/. >>>> Such "scans" as you mention, happen to everyone, all the time, from >>>> ever-changing IP addresses located all over the world. Some of those >>>> "scans" may come from the infected PC of your grandmother, and she does >> not >>>> even know about it. >>>> >>>> There is no guarantee, and no indication or proof so far, that /these/ >>>> scans are even related to "the other thing" which happens on your >>>> webserver, which looked much more focused. >>>> >>>> So do not just bundle them together as being the same thing, until you >>>> have some real data that shows for example that these different things >> all >>>> come from the same IP addresses. >>>> >>>> And one more thing, also finally until you come back with some real >> data : >>>> I am not saying that your application "scans your server". What I am >>>> saying is that, maybe, by chance or by design, the attackers have found >> a >>>> URL which goes to your application, and which causes your application to >>>> keep tomcat and/or Apache busy for a long time. >>>> And that maybe /that/ is the problem you should be looking for, and not >>>> some hypothetical bug in Apache httpd or tomcat. >>>> >>>> >>>> >>>>> kindly regards, >>>>> artur >>>>> >>>>> 2016-11-28 21:33 GMT+01:00 André Warnier (tomcat) <a...@ice-sa.com>: >>>>> >>>>> On 28.11.2016 20:34, Jaaz Portal wrote: >>>>>> >>>>>> hi mark, >>>>>>> yes, i understand now what slowloris attack is. >>>>>>> maybe it was this maybe *this one based on * * mod_proxy denial of >>>>>>> service * >>>>>>> CVE-2014-0117 <http://cve.mitre.org/cgi-bin/ >>>>>>> cvename.cgi?name=CVE-2014-0117> >>>>>>> >>>>>>> >>>>>> You keep on saying this, but the description of that vulnerability of >>>>>> *Apache httpd*, and the symptoms which you described, *do not match*. >>>>>> You described the problem as ocurring in Apache tomcat, which in your >>>>>> case >>>>>> is sitting as a back-end, *behind* Apache httpd. And restarting tomcat >>>>>> cured the problem. >>>>>> >>>>>> The CVE above applies to Apache httpd, and describes how an attacker >>>>>> could >>>>>> attack Apache httpd and cause *its children* processes to crash (the >>>>>> children processes of Apache httpd), by leading them to consume a lot >> of >>>>>> memory and crash with an out-of-memory error. >>>>>> Granted, the problem occurred in the mod_proxy module of Apache httpd; >>>>>> but >>>>>> it was httpd which crashed, not tomcat. >>>>>> And tomcat processes are not "Apache httpd children processes" in any >>>>>> understanding of the term. >>>>>> >>>>>> As far as I remember, you never mentioned Apache httpd crashing. You >>>>>> mentioned "the pool" getting full or satured or something like that, >>>>>> without ever describing properly what you meant by "the pool". >>>>>> >>>>>> As far as I am concerned, according to all the relatively unspecific >>>>>> information which you have previously provided : >>>>>> 1) the attack - if that is what it is/was - is definitely NOT related >> to >>>>>> the CVE which you have repeatedly mentioned >>>>>> 2) it is apparently not a "classical" DoS or "slowloris DoS" directed >> at >>>>>> your front-end Apache. Instead, it seems that the requests are >> properly >>>>>> received by Apache, properly decoded by Apache, and then whatever >> Apache >>>>>> proxy module you are using (mod_proxy_http, mod_proxy_ajp or mod_jk) >> is >>>>>> properly forwarding these requests to a back-end tomcat; and it is at >> the >>>>>> level of that back-end tomcat that the requests never seem to end, >> and in >>>>>> the end paralyse your tomcat server (and later on maybe your Apache >> httpd >>>>>> server too, because it is also waiting for tomcat to respond). >>>>>> >>>>>> So your very way of describing the problem, in terms of "first we used >>>>>> this proxy module, and then they exploited the vulnerability so and >> so; >>>>>> then we changed the proxy module, and they exploited that too; etc.." >>>>>> seems to not have anything to do with the problem per se, and (I >> believe) >>>>>> confuses everyone, including yourself. >>>>>> >>>>>> It is not that "they" exploited different vulnerabilities of various >>>>>> httpd >>>>>> proxy modules, one after the other. Each of these proxy modules was >> doing >>>>>> its job properly, and forwarding valid HTTP requests properly to >> tomcat. >>>>>> When you changed from one proxy module to another, you did not really >>>>>> change anything in that respect, because any proxy module would do the >>>>>> same. >>>>>> >>>>>> But in all cases, what did not change, was the tomcat behind the >>>>>> front-end, and the application running on that tomcat. So the >> presumed >>>>>> attackers did not have to change anything, they just kept on sending >> the >>>>>> same requests, because they were really targeting your back-end >> tomcat or >>>>>> the tomcat application in it, no matter /how/ you were forwarding >>>>>> requests >>>>>> from Apache httpd to tomcat. >>>>>> >>>>>> So either it is tomcat itself, which has a problem with some request >> URLs >>>>>> which do not bother Apache httpd (possible, but statistically >> unlikely), >>>>>> or >>>>>> it is the application which runs in tomcat that has such a problem >>>>>> (statistically, much more likely). >>>>>> >>>>>> we do not know yet >>>>>> >>>>>>> >>>>>>> we have setup more logging and are waiting for them to attack once >> again >>>>>>> >>>>>>> >>>>>> Yes, that is the right thing to do. Before deciding what the problem >> may >>>>>> be, and what you can do about it, the first thing you need is *data*. >>>>>> You >>>>>> need to know >>>>>> - which request URL(s?) cause that problem >>>>>> - which IPs these requests come from (always the same ? multiple IPs >> that >>>>>> change all the time ? how many ? can these IPs be valid/expected >> clients >>>>>> or >>>>>> not ? do these IPs look like some "coordinated group" ?) >>>>>> - how many such requests there may be during some period of time (10, >>>>>> 100, >>>>>> 1000, more ?) >>>>>> - if these URLs result in passing the request to tomcat >>>>>> - what tomcat application (if any) they are directed to >>>>>> - if so, when that application receives such a request, what is it >>>>>> supposed to do ? does it do it properly ? how long does it need, to >>>>>> respond >>>>>> to such a request ? >>>>>> >>>>>> You also need to ask yourself a question : is the application which >> you >>>>>> run inside tomcat something that you designed yourself (and which >> hackers >>>>>> are unlikely to know well-enough to find such a URL which paralyses >> your >>>>>> server) ? or is it some well-known third-party java application which >> you >>>>>> are running (and for which would-be attackers would be much more >> likely >>>>>> to >>>>>> know exactly such a bug) ? >>>>>> >>>>>> >>>>>> anyway, thank you for all informations, it was very useful and >>>>>>> educational >>>>>>> reading for all of us >>>>>>> >>>>>>> best wishes, >>>>>>> artur >>>>>>> >>>>>>> 2016-11-28 19:46 GMT+01:00 Mark Eggers <its_toas...@yahoo.com.invalid >>> : >>>>>>> >>>>>>> Jaaz, >>>>>>> >>>>>>>> >>>>>>>> On 11/27/2016 2:46 PM, André Warnier (tomcat) wrote: >>>>>>>> >>>>>>>> On 27.11.2016 19:03, Jaaz Portal wrote: >>>>>>>>> >>>>>>>>> 2016-11-27 18:30 GMT+01:00 André Warnier (tomcat) <a...@ice-sa.com>: >>>>>>>>>> >>>>>>>>>> On 27.11.2016 14:26, Jaaz Portal wrote: >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> hi, >>>>>>>>>>> >>>>>>>>>>>> everything i know so far is just this single log line that >> appeared >>>>>>>>>>>> in >>>>>>>>>>>> apache error.log >>>>>>>>>>>> >>>>>>>>>>>> [Fri Nov 25 13:08:00.647835 2016] [mpm_event:error] [pid >> 13385:tid >>>>>>>>>>>> 1397934896385 >>>>>>>>>>>> 92] AH00484: server reached MaxRequestWorkers setting, consider >>>>>>>>>>>> >>>>>>>>>>>> raising >>>>>>>>>>> >>>>>>>>>> >>>>>>>> the >>>>>>>>> >>>>>>>>>> MaxR >>>>>>>>>>>> equestWorkers setting >>>>>>>>>>>> >>>>>>>>>>>> there was nothing else, just this strange line >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> This is not a "strange" line. It is telling you something. >>>>>>>>>>> One problem is that you seem convinced in advance, without >> serious >>>>>>>>>>> proof, >>>>>>>>>>> that there is a "bug" or a vulnerability in httpd or tomcat. >>>>>>>>>>> Read the explanation of the httpd parameter, here : >>>>>>>>>>> http://httpd.apache.org/docs/2.4/mod/mpm_common.html#maxrequ >>>>>>>>>>> estworkers >>>>>>>>>>> and try to understand it. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> I understand it very well. We are serving no more that 500 >> clients >>>>>>>>>> per >>>>>>>>>> day >>>>>>>>>> so there was no other option that some kind of attack. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> About the "bug" or "vulnerability" : a webserver is supposed to >> serve >>>>>>>>>> HTTP >>>>>>>>>> >>>>>>>>>> requests from clients. That is what you expect of it. It has no >>>>>>>>>>> choice but >>>>>>>>>>> to accept any client connection and request, up to the maximum it >>>>>>>>>>> can >>>>>>>>>>> handle considering its configuration and the capacity of the >> system >>>>>>>>>>> on >>>>>>>>>>> which it runs. That is not a bug, it is a feature. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> We have some weeks ago come under attack from some Polish group. >> It >>>>>>>>>>> >>>>>>>>>> was >>>>>>>>>> first bind that was DoS'ed, we was running on stable Debian so i >>>>>>>>>> updated >>>>>>>>>> bind to latest version. It did not helped. They has dos'ed it so >> we >>>>>>>>>> switched to other dns provider. That has helped. >>>>>>>>>> >>>>>>>>>> Then they exploited some well know vulnerability in mod_proxy. We >>>>>>>>>> have >>>>>>>>>> updated apache to the latest but again they has exploited it, so >> we >>>>>>>>>> have >>>>>>>>>> switched to mod_jk. And then guess what. They exploited it too so >> i >>>>>>>>>> decided >>>>>>>>>> to write to this list looking for help before trying jetty. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> The normal Apache httpd access log, will log a request only when >> it >>>>>>>>>>> is >>>>>>>>>>> finished. If the request never finishes, it will not get logged. >>>>>>>>>>> That may be why you do not see these requests in the log. >>>>>>>>>>> But have a look at this Apache httpd module : >>>>>>>>>>> http://httpd.apache.org/docs/2.4/mod/mod_log_forensic.html >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> ok, thanks, will take care >>>>>>>>>> >>>>>>>>>> Note : that is also why I was telling you to enable the mod_jk >> log, >>>>>>>>>> and to >>>>>>>>>> >>>>>>>>>> examine it. >>>>>>>>>>> Because mod_jk will also log information before the request >>>>>>>>>>> produces a >>>>>>>>>>> response. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> and server hanged. >>>>>>>>>>> >>>>>>>>>>> Again, /what/ is "hanged" ? Apache httpd, or tomcat ? >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Apache was accepting connection but not processed it. After >> restart >>>>>>>>>> of >>>>>>>>>> tomcat server it worked again. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Also in >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> access logs there are no clues that it was under any heavy load. >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> after around hour after discovering that our server hanged-out >> we >>>>>>>>>>>> have >>>>>>>>>>>> restarted tomcat server >>>>>>>>>>>> and it worked again >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Yes, because that will close all connections between Apache >> httpd >>>>>>>>>>> and >>>>>>>>>>> tomcat, and abort all requests that are in the process of being >>>>>>>>>>> processed >>>>>>>>>>> by tomcat. So mod_jk will get an error from tomcat, and will >> report >>>>>>>>>>> an >>>>>>>>>>> error to httpd, and httpd will communicate that error to the >>>>>>>>>>> clients, >>>>>>>>>>> and >>>>>>>>>>> close their connection. >>>>>>>>>>> It still does not tell you what the problem was. >>>>>>>>>>> The only thing that it suggests, is that the "bad" requests >> actually >>>>>>>>>>> make >>>>>>>>>>> it all the way to tomcat. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> correct >>>>>>>>>> >>>>>>>>>> i will enable logs that you has pointed out and we will look what >> i >>>>>>>>>> will >>>>>>>>>> catch >>>>>>>>>> however i think we have only one chance, as if the solution we has >>>>>>>>>> found >>>>>>>>>> out (connection_timeout + mod_bn) >>>>>>>>>> will work they will stop exploiting it >>>>>>>>>> >>>>>>>>>> thank you very much for all the help and explanations >>>>>>>>>> i will report to the list new facts once they will attack us again >>>>>>>>>> >>>>>>>>>> best regards, >>>>>>>>>> artur >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Ok, but also read this e.g. : >>>>>>>>> https://www.corero.com/blog/695-going-after-the-people- >>>>>>>>> >>>>>>>>> behind-ddos-attacks.html >>>>>>>> >>>>>>>> >>>>>>>>> Attempts to bring down a site by DoS attacks is a crime, in most >>>>>>>>> places.. >>>>>>>>> >>>>>>>>> You can report it, while at the same time trying to defend yourself >>>>>>>>> against it. >>>>>>>>> >>>>>>>>> It is also relatively easy, and quite inexpensive in terms of >> system >>>>>>>>> resources, to run a small shell script which takes a list every few >>>>>>>>> seconds of the connections to the port of your webserver, and which >>>>>>>>> IPs >>>>>>>>> they are coming *from*. >>>>>>>>> E.g. >>>>>>>>> First try the netstat command, to see what it lists, like : >>>>>>>>> # netstat -n --tcp | more >>>>>>>>> >>>>>>>>> Then you will want to filter this a bit, to only consider >> established >>>>>>>>> connections to your webserver, for example : >>>>>>>>> # netstat -n --tcp | grep ":80" | grep "ESTABLISHED" >>>>>>>>> >>>>>>>>> Then you will want to send this to a logfile, regularly, like this >> : >>>>>>>>> >>>>>>>>> # date >> some_file.log >>>>>>>>> # netstat -n --tcp | grep ":80" | grep "ESTABLISHED" >> >> some_file.log >>>>>>>>> (repeat every 3 seconds) >>>>>>>>> >>>>>>>>> This will not generate GB of logfiles, and it will tell you, when >> the >>>>>>>>> problem happens, how many connections there are exactly to your >>>>>>>>> webserver, and where they are coming from. >>>>>>>>> Then later you can further analyse this information.. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>>> i think that setting connection-timeout and limiting the number of >>>>>>>>>> >>>>>>>>>>> clients >>>>>>>>>>>> by mod_bd i will >>>>>>>>>>>> have effect that next time somebody will try this exploit it >> will >>>>>>>>>>>> >>>>>>>>>>>> block >>>>>>>>>>> >>>>>>>>>> >>>>>>>> his >>>>>>>>> >>>>>>>>>> access to the site >>>>>>>>>>>> for minute or two, pretty good holistic solution i would say >>>>>>>>>>>> >>>>>>>>>>>> still, it seems that there is serious vulnerability somewhere in >>>>>>>>>>>> apache, >>>>>>>>>>>> mod_jk or tomcat >>>>>>>>>>>> i would like to help find it out but need some hints which debug >>>>>>>>>>>> options >>>>>>>>>>>> enable to catch the bad guys >>>>>>>>>>>> when they will try next time >>>>>>>>>>>> >>>>>>>>>>>> best regards, >>>>>>>>>>>> artur >>>>>>>>>>>> >>>>>>>>>>>> 2016-11-27 13:58 GMT+01:00 André Warnier (tomcat) < >> a...@ice-sa.com>: >>>>>>>>>>>> >>>>>>>>>>>> On 27.11.2016 13:23, Jaaz Portal wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>>> hi Andre, >>>>>>>>>>>>> >>>>>>>>>>>>> thank you very much this was very educative but in my case it >> is >>>>>>>>>>>>>> little >>>>>>>>>>>>>> bit >>>>>>>>>>>>>> different. >>>>>>>>>>>>>> The server is no flooded, there is maybe dozen of very >>>>>>>>>>>>>> sophisticated >>>>>>>>>>>>>> connections that somehow hangs apache workers threads >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Can you be a bit more specific ? >>>>>>>>>>>>>> >>>>>>>>>>>>> When you say "apache workers threads", do you mean threads in >>>>>>>>>>>>> Apache >>>>>>>>>>>>> httpd, or threads in Apache Tomcat ? (both are Apache >> webservers, >>>>>>>>>>>>> so it >>>>>>>>>>>>> is >>>>>>>>>>>>> difficult to tell what you are talking about, unless you are >> very >>>>>>>>>>>>> precise). >>>>>>>>>>>>> >>>>>>>>>>>>> Let me give you some additional explanations, and maybe you can >>>>>>>>>>>>> >>>>>>>>>>>>> figure >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> out >>>>>>>>> >>>>>>>>>> exactly where it "hangs". >>>>>>>>>>>>> >>>>>>>>>>>>> From the Apache httpd front-end point of view, mod_jk (the >>>>>>>>>>>>> connector to >>>>>>>>>>>>> Apache Tomcat) is basically one among other "response >> generators". >>>>>>>>>>>>> Apache >>>>>>>>>>>>> httpd does not "know" that behind mod_jk, there is one or more >>>>>>>>>>>>> Tomcat >>>>>>>>>>>>> servers. Apache httpd receives the original client request, >> and >>>>>>>>>>>>> depending >>>>>>>>>>>>> on the URL of the request, it will pass it to mod_jk or to >> another >>>>>>>>>>>>> response >>>>>>>>>>>>> generator, to generate the response to the request. >>>>>>>>>>>>> That mod_jk in the background is using a Tomcat server to >> actually >>>>>>>>>>>>> generate the response, is none of the business of Apache httpd, >>>>>>>>>>>>> and >>>>>>>>>>>>> >>>>>>>>>>>>> it >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> does >>>>>>>>> >>>>>>>>>> not care. All it cares about, is to actually receive the response >>>>>>>>>>>>> >>>>>>>>>>>>> from >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> mod_jk, and pass it back to the client. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>> If httpd passes a request to mod_jk, it is because you have >>>>>>>>>>>>> specified in >>>>>>>>>>>>> the Apache configuration, the type of URL that it should pass >> to >>>>>>>>>>>>> mod_jk.. >>>>>>>>>>>>> That happens via your "JkMount (URL pattern)" directives in >> Apache >>>>>>>>>>>>> httpd. >>>>>>>>>>>>> >>>>>>>>>>>>> Of course Apache httpd will not pass a request to mod_jk, >> before >>>>>>>>>>>>> it >>>>>>>>>>>>> has >>>>>>>>>>>>> received at least the URL of the request, and analysed it to >>>>>>>>>>>>> >>>>>>>>>>>>> determine >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> *if* >>>>>>>>> >>>>>>>>>> it should pass it to mod_jk (*). >>>>>>>>>>>>> >>>>>>>>>>>>> If the mod_jk logging is enabled, you can see in it, exactly >>>>>>>>>>>>> *which* >>>>>>>>>>>>> requests are passed to mod_jk and to Tomcat. >>>>>>>>>>>>> Do you know *which* requests, from which clients, cause this >>>>>>>>>>>>> "thread >>>>>>>>>>>>> hanging" symptom ? >>>>>>>>>>>>> Once you would know this, maybe you can design a strategy to >> block >>>>>>>>>>>>> specifically these requests. >>>>>>>>>>>>> >>>>>>>>>>>>> and the effect is permanent. Quickly the pool is exhausted >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> which pool exactly ? >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> and the only >>>>>>>>>>>>> >>>>>>>>>>>>> solution that works is to restart tomcat. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>>> I think it is a bug similar to this one from mod_proxy: >>>>>>>>>>>>>> https://tools.cisco.com/security/center/viewAlert.x?alertId= >>>>>>>>>>>>>> 34971 >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Maybe, maybe not. As long as we do not know what the requests >>>>>>>>>>>>>> are, >>>>>>>>>>>>>> that >>>>>>>>>>>>>> >>>>>>>>>>>>>> block things, we do not know this. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> I think also that your solution with setting connectionTimeout >>>>>>>>>>>>> will >>>>>>>>>>>>> solve >>>>>>>>>>>>> >>>>>>>>>>>>> the problem, at least partially. THANK YOU. >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Same thing, we do not know this yet. It was only giving this >>>>>>>>>>>>>> >>>>>>>>>>>>> explanation, >>>>>>>>>>>>> to help you think about where the problem may be. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> I would like to help you further investigate this issue, as our >>>>>>>>>>>>> >>>>>>>>>>>>> server >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> comes under such attack once or twice in a week. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Other than giving you hints, there is not much I or anyone >> else >>>>>>>>>>>>>> can do >>>>>>>>>>>>>> >>>>>>>>>>>>>> to >>>>>>>>>>>>> help. You are the one with control of your servers and >> logfiles, >>>>>>>>>>>>> so >>>>>>>>>>>>> you >>>>>>>>>>>>> have to investigate and provide more precise information. >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> (*) actually, to be precise, Apache httpd passes *all* >> requests to >>>>>>>>>>>>> mod_jk, >>>>>>>>>>>>> to ask it "if it wants that request". mod_jk then accepts or >>>>>>>>>>>>> >>>>>>>>>>>>> declines, >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> depending on the JkMount instructions. If mod_jk declines, then >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>> Apache >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>> httpd will ask the next response generator if it wants this request, >>>>>>>>> >>>>>>>>>> etc... >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> best regards, >>>>>>>>>>>>> >>>>>>>>>>>>> artur >>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> 2016-11-27 12:46 GMT+01:00 André Warnier (tomcat) < >> a...@ice-sa.com >>>>>>>>>>>>>>> : >>>>>>>>>>>>>> >>>>>>>>>>>>>> Hi. >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>>> Have a look that the indicated parameters in the two pages >>>>>>>>>>>>>>> below.. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> You may be the target of such a variant of DDoS attack : many >>>>>>>>>>>>>>> clients >>>>>>>>>>>>>>> open >>>>>>>>>>>>>>> a TCP connection to your server (front-end), but then never >>>>>>>>>>>>>>> sends >>>>>>>>>>>>>>> a >>>>>>>>>>>>>>> HTTP >>>>>>>>>>>>>>> request on that connection. In the meantime, the server >> accepts >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> the >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>> TCP >>>>>>>>> >>>>>>>>>> connection, and passes it on to a "child" process or thread for >>>>>>>>>>>>>>> processing. The child then waits for the HTTP request line >> to >>>>>>>>>>>>>>> arrive >>>>>>>>>>>>>>> on >>>>>>>>>>>>>>> the connection (during a certain time), but it never arrives. >>>>>>>>>>>>>>> After a >>>>>>>>>>>>>>> while, this triggers a timeout (see below), but the standard >>>>>>>>>>>>>>> value of >>>>>>>>>>>>>>> that >>>>>>>>>>>>>>> timeout may be such that in the meantime, a lot of other >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> connections >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>> have >>>>>>>>> >>>>>>>>>> been established by other such nefarious clients, so a lot of >>>>>>>>>>>>>>> resources >>>>>>>>>>>>>>> of >>>>>>>>>>>>>>> the webserver are tied up, waiting for something that will >> never >>>>>>>>>>>>>>> come.. >>>>>>>>>>>>>>> Since there is never any real request sent on the connection, >>>>>>>>>>>>>>> you >>>>>>>>>>>>>>> would >>>>>>>>>>>>>>> (probably) not see this in the logs either. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> The above is the basic mechanism of such an attack. There >> may >>>>>>>>>>>>>>> be >>>>>>>>>>>>>>> variations, such as the client not "not sending" a request >> line, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> but >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>> sending it extremely slowly, thus achieving perhaps similar kinds >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>>> of >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>> effects. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>>> As someone pointed out, it is quite difficult to do something >>>>>>>>>>>>>>> about >>>>>>>>>>>>>>> this >>>>>>>>>>>>>>> at the level of the webserver itself, because by the time you >>>>>>>>>>>>>>> would do >>>>>>>>>>>>>>> something about it, the resources have already been consumed >> and >>>>>>>>>>>>>>> your >>>>>>>>>>>>>>> server is probably already overloaded. >>>>>>>>>>>>>>> There are specialised front-end devices and software >> available, >>>>>>>>>>>>>>> to >>>>>>>>>>>>>>> detect >>>>>>>>>>>>>>> and protect against this kind of attack. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> You may want to have a look at the following parameters, but >>>>>>>>>>>>>>> make >>>>>>>>>>>>>>> sure >>>>>>>>>>>>>>> to >>>>>>>>>>>>>>> read the caveats (side-effects, interlocking timeouts etc.), >>>>>>>>>>>>>>> otherwise >>>>>>>>>>>>>>> you >>>>>>>>>>>>>>> may do more harm than good. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Another thing : the settings below are for Apache Tomcat, >> which >>>>>>>>>>>>>>> in your >>>>>>>>>>>>>>> case is the back-end. It would of course be much better to >>>>>>>>>>>>>>> detect >>>>>>>>>>>>>>> and >>>>>>>>>>>>>>> eliminate this at the front-end, or even before. I had a >> look >>>>>>>>>>>>>>> at >>>>>>>>>>>>>>> the >>>>>>>>>>>>>>> Apache httpd documentation, and could not find a >> corresponding >>>>>>>>>>>>>>> parameter. >>>>>>>>>>>>>>> But I am sure that it must exist. You may want to post this >> same >>>>>>>>>>>>>>> question >>>>>>>>>>>>>>> on the Apache httpd user's list for a better response. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Tomcat configuration settings : >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> AJP Connector : (http://tomcat.apache.org/tomc >>>>>>>>>>>>>>> at-8.5-doc/config/ajp.html# >>>>>>>>>>>>>>> Standard_Implementations) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> connectionTimeout >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> The number of milliseconds this Connector will wait, after >>>>>>>>>>>>>>> accepting a >>>>>>>>>>>>>>> connection, for the request URI line to be presented. The >>>>>>>>>>>>>>> default >>>>>>>>>>>>>>> value >>>>>>>>>>>>>>> for >>>>>>>>>>>>>>> AJP protocol connectors is -1 (i.e. infinite). >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> (You could for example try to set this to 3000 >> (milliseconds) or >>>>>>>>>>>>>>> even >>>>>>>>>>>>>>> lower. That should be more than enough for any legitimate >> client >>>>>>>>>>>>>>> so >>>>>>>>>>>>>>> send >>>>>>>>>>>>>>> the HTTP request line. Note however that by doing this at >> the >>>>>>>>>>>>>>> Tomcat >>>>>>>>>>>>>>> level, you will probably move the problem to the Apache >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> httpd/mod_jk >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>> level. But at least it might confirm that this is the problem >>>>>>>>> >>>>>>>>>> that you >>>>>>>>>>>>>>> are >>>>>>>>>>>>>>> seeing. The mod_jk logfile at the httpd level may give you >> some >>>>>>>>>>>>>>> hints >>>>>>>>>>>>>>> there.) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> HTTP Connector : (http://tomcat.apache.org/tomc >>>>>>>>>>>>>>> at-8.5-doc/config/http.html#Standard_Implementation) >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> connectionTimeout >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> The number of milliseconds this Connector will wait, after >>>>>>>>>>>>>>> accepting a >>>>>>>>>>>>>>> connection, for the request URI line to be presented. Use a >>>>>>>>>>>>>>> value >>>>>>>>>>>>>>> of -1 >>>>>>>>>>>>>>> to >>>>>>>>>>>>>>> indicate no (i.e. infinite) timeout. The default value is >> 60000 >>>>>>>>>>>>>>> (i.e. >>>>>>>>>>>>>>> 60 >>>>>>>>>>>>>>> seconds) but note that the standard server.xml that ships >> with >>>>>>>>>>>>>>> Tomcat >>>>>>>>>>>>>>> sets >>>>>>>>>>>>>>> this to 20000 (i.e. 20 seconds). Unless disableUploadTimeout >> is >>>>>>>>>>>>>>> set to >>>>>>>>>>>>>>> false, this timeout will also be used when reading the >> request >>>>>>>>>>>>>>> body (if >>>>>>>>>>>>>>> any). >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> On 26.11.2016 09:57, Jaaz Portal wrote: >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> hi, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> sorry, its mod_jk no jk2, my typo. All at latest versions. We >>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> tried >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>> with >>>>>>>>> >>>>>>>>>> mod proxy too. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> There is no flood of the server. Nobody is flooding us, they >>>>>>>>>>>>>>>> use >>>>>>>>>>>>>>>> some >>>>>>>>>>>>>>>> specific connections after which pool of apache workers is >>>>>>>>>>>>>>>> exhausted >>>>>>>>>>>>>>>> and >>>>>>>>>>>>>>>> blocked >>>>>>>>>>>>>>>> and we need to restart tomcat server. >>>>>>>>>>>>>>>> It is some kind of exploit but do not know how to log it to >>>>>>>>>>>>>>>> obtain >>>>>>>>>>>>>>>> details. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> i had put a limit on connections per client with hope that >> this >>>>>>>>>>>>>>>> will >>>>>>>>>>>>>>>> help >>>>>>>>>>>>>>>> but once again, it is not a flood. >>>>>>>>>>>>>>>> They open several connections that are not dropped by apache >>>>>>>>>>>>>>>> when they >>>>>>>>>>>>>>>> disconnect. This way whole pool is quickly exhausted and the >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> server >>>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>> broken. >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>>>> i would like to help you to figure details of this attack >> but >>>>>>>>>>>>>>>> this is >>>>>>>>>>>>>>>> production server so it is impossible to much debugging >> options >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> best, >>>>>>>>>>>>>>>> artur >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> 2016-11-25 23:44 GMT+01:00 Niranjan Babu Bommu < >>>>>>>>>>>>>>>> niranjan.bo...@gmail.com >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> : >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> you can find who is flooding site in apache access.log and >>>>>>>>>>>>>>>>> block >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> them >>>>>>>>>>>>>>>> in >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> firewall. >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> ex to find the IP: >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> cat /var/log/apache2/access.log |cut -d' ' -f1 |sort |uniq >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> -c|sort >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>> -gr >>>>>>>>> >>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> On Fri, Nov 25, 2016 at 8:42 AM, Jaaz Portal >>>>>>>>>>>>>>>>> <jaazpor...@gmail.com> >>>>>>>>>>>>>>>>> wrote: >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> hi, >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> we are from some weeks struggling with some Polish hackers >>>>>>>>>>>>>>>>> that >>>>>>>>>>>>>>>>> are >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> bringing our server down. After updating apache to latest >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> version >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> >>>>>>>> >>>>>>>>> (2.4.23) >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> and tomcat (8.0.38) available for debian systems we still >>>>>>>>>>>>>>>>> cannot >>>>>>>>>>>>>>>>> secure >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> our >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> server. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Today it has stopped to respond again and we needed to >> restart >>>>>>>>>>>>>>>>>> tomcat >>>>>>>>>>>>>>>>>> process to get it back alive. >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> There is no too much clues in the logs. The apache >> error.log >>>>>>>>>>>>>>>>>> gives >>>>>>>>>>>>>>>>>> just >>>>>>>>>>>>>>>>>> this line: >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> [Fri Nov 25 13:08:00.647835 2016] [mpm_event:error] [pid >>>>>>>>>>>>>>>>>> 13385:tid >>>>>>>>>>>>>>>>>> 1397934896385 >>>>>>>>>>>>>>>>>> 92] AH00484: server reached MaxRequestWorkers setting, >>>>>>>>>>>>>>>>>> consider >>>>>>>>>>>>>>>>>> raising >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> the >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> MaxR >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> equestWorkers setting >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> seems that somehow tomcat, mod-jk2 or even apache is >>>>>>>>>>>>>>>>>> vulnerable to >>>>>>>>>>>>>>>>>> some >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> new >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> exploit, as we certainly does not have such traffic that >>>>>>>>>>>>>>>>> would >>>>>>>>>>>>>>>>> block >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> our >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> server otherwise >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> for now we have increased MaxRequestWorkers and we have >>>>>>>>>>>>>>>>>> limited >>>>>>>>>>>>>>>>>> number >>>>>>>>>>>>>>>>>> of >>>>>>>>>>>>>>>>>> connections from one client to 5 by mod_bw and limited >> number >>>>>>>>>>>>>>>>>> of >>>>>>>>>>>>>>>>>> simultaneous connections from one ip by iptables but does >> not >>>>>>>>>>>>>>>>>> know >>>>>>>>>>>>>>>>>> if >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> this >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> will help >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> best regards, >>>>>>>>>>>>>>>>>> artur >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> *Thanks* >>>>>>>>>>>>>>>>> *Niranjan* >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> This sounds like a variant of the slowloris attack. >>>>>>>> >>>>>>>> This type of attack doesn't take a large number of clients or >> consume a >>>>>>>> large amount of bandwidth. >>>>>>>> >>>>>>>> Basically, the maximum number of connections are made to the server, >>>>>>>> and >>>>>>>> just enough data is sent to each connection in order to not trigger >> the >>>>>>>> timeout. André has explained this in more detail earlier in the >> thread. >>>>>>>> Search for "slowloris attack" for more information. >>>>>>>> >>>>>>>> There are several ways of mitigating this type of attack. >>>>>>>> >>>>>>>> As André has mentioned, placing a dedicated device in front of your >>>>>>>> systems is often the best way. Lots of benefits (platform neutral, >> no >>>>>>>> stress on your current servers), and some issues (cost, placement / >>>>>>>> access may be an issue with hosted solutions). >>>>>>>> >>>>>>>> However, there are Apache HTTPD modules that can help mitigate these >>>>>>>> types of attacks. Some of them are: >>>>>>>> >>>>>>>> mod_reqtimeout (should be included by default in your Apache HTRPD >> 2.4) >>>>>>>> mod_qos (quality of service module) >>>>>>>> mod_security (application firewall with lots of security rules) >>>>>>>> >>>>>>>> Do a quick search on "slowloris attack apache httpd 2.4" to get some >>>>>>>> ideas. >>>>>>>> >>>>>>>> All of them will probably place additional load on your Apache HTTPD >>>>>>>> server, so make sure that the platform is robust enough to manage >> the >>>>>>>> additional load. >>>>>>>> >>>>>>>> There is also a beta version of the mod_security module written as a >>>>>>>> servlet filter. It should be possible to build this and configure >> the >>>>>>>> filter in Tomcat's default web.xml ($CATALINA_BASE/conf/web.xml). >> I've >>>>>>>> not tried this. Also, the code base hasn't seen any activity for 3 >>>>>>>> years. >>>>>>>> >>>>>>>> Do a quick search on "modsecurity servlet filter" to find out more >>>>>>>> about >>>>>>>> the servlet filter version of mod_security. >>>>>>>> >>>>>>>> In short, there appear to be some ways to mitigate the attack. >>>>>>>> >>>>>>>> . . . just my two cents >>>>>>>> /mde/ >> >> >> >> >
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