A distributed denial of service attack (DDoS) occurs when multiple systems flood the bandwidth or resources of a targeted system, usually one or more web servers. These systems are compromised by attackers using a variety of methods.

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18 views

.htaccess rules to stop DDoS POST flooding

We're under a distributed denial of service attack from traffic that looks like this: 49.146.161.175 - - [11/Jul/2014:00:43:42 -0400] "POST / HTTP/1.1" 500 557 "-" "Mozilla/4.0 (compatible; MSIE 6.0; ...
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2answers
26 views

blocking udp attack ip with iptables

I was trying to block an ip of ( network stresser tool - a ddos websites selling ddos bots by seconds online ) the first one i was trying to block with iptables : iptables -A INPUT -d 173.193.26.73 ...
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1answer
21 views

ddos mitigation , traffic spike [on hold]

since last week we are having a traffic spike that take down our server, in our traffic stats we see this at the time of the attack Current Out: 98.2 Mb/s (98.2%) the server gets down so i can't ...
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1answer
47 views

Does “TARPIT” have any known vulnerabilities or downsides?

TARPIT can be used to waste an attacker's resources, thus slowing down his attacks and lowering his ability to attack other hosts... looks like a good idea. It is provided as a Netfilter addon and ...
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1answer
12 views

how to reduce chances of getting syn flood on mac os x? [on hold]

Are mechanisms like syn cookies enabled in Mac OS X by default? Unlike Linux, there is no net.ipv4.tcp_syncookies in sysctl, so how do I turn them on in Mac OS X if it is not on already.
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2answers
57 views

Does CloudFlare make a site a greater potential DDOS target?

CloudFlare has gotten a lot of press recently as protecting businesses from DDOS attacks. But from looking at their twitter feed, it looks like they are targeted every day, and large segments of their ...
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3answers
119 views

My webserver is getting flooded with invalid requests

My webserver (nginx) keeps getting requests like this: 23.244.104.206 - - [15/Jun/2014:21:21:47 -0400] "GET ...
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0answers
25 views

How do you protect your <appid>.appspot.com domain from DDOS attack?

If I want to use CloudFlare to help protect my GAE app via it's custom domain, I still am vulnerable to attacks directly on the .appspot.com domain. How do I mitigate that? I could force redirect ...
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0answers
9 views

Repeated installation of malicious software to do outbound DDOS attack [duplicate]

We have a Ubuntu Vitual Private Server hosted by a Canadian company. Out VPS was affected to do "outbound DDOS attack" as reported by server security team. There are 4 files in /boot looks like ...
0
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1answer
132 views

iptables to allow input and output traffic to and from web server only

I have an Elastic Search server which seems to have been exploited (it's being used for a DDoS attack having had NO firewall for about a month). As a temporary measure while I create a new one I was ...
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2answers
30 views

How to find the count of Apache workers' at a given point for shared IPs?

One can find the number of Apache workers an IP address is consuming at an instantaneous point in time by executing: netstat -pantu | grep :80 |sort | uniq -c |grep <IP_HERE, eg: 192.168> | wc ...
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2answers
66 views

Is it possible to prevent DDoS attacks? [closed]

I recently read that certain industries—including the one I work in—are more likely than others to be targeted by a DDoS attack. Can you give me some tips on how to prevent DDoS attacks?
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1answer
168 views

SynFlood attack, spoofed IPs, syncookies mitigation

Due to a recent increase in SynFlood attacks on my company's systems i've been testing by Syn flooding the hosts myself to see how easy they are to disrupt, and the answer is 'quite easy'. By using a ...
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0answers
124 views

Curl Sourced DDoS: How to detect it & how to stop?

Okay, an Ubuntu server I manage fell victim to a DDoS attack today. Usually this is unpleasant but not that big a deal. A few high server load moments & then it passes. Today was clearly ...
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0answers
259 views

High outbound network traffic on Tomcat under process nodeJR

We are investigating high outbound traffic on Tomcat servers hosted on AWS instances. The specific question I have is what the process nodeJR is - and how it could get installed under Tomcat? The ...
1
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0answers
38 views

Multiple DDOS protection interfaces merging on one TS server

The problem I have is I have 3 DDOS protection interfaces from a multi homed DDOS protection solution and teamspeak is refusing to return packets via the correct interface (aka the one that sent it ...
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0answers
66 views

Apache2 php-cgi processes, how to limit them?

I have a 32gig ram dedicated server running on Ubuntu 12.04 with ISPConfig / Apache configuration. The thing is, anyone can take the site down simply by holding down F5 button for 20 seconds causing ...
2
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1answer
191 views

Outbound DDOS Attacks Being Run from Our Server

We run a mail server (postfix/dovecot/centos 6.4). The hardware is based on a supermicro chasis with IPMI features. It also runs a web interface for accesisng mails(Apache web server ) Recently our ...
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1answer
185 views

Apache logs flooded with connections - “(via ggpht.com GoogleImageProxy)”

My server was running on 100% CPU and looking at the Apache logs I saw hundreds of thousands of connections that looked like this: 10.190.45.31 - - [13/Mar/2014:15:29:02 +0000] "GET SOMETHING ...
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1answer
115 views

blocking all countries except 4 at vlan level, will cisco asa 5505 hold?

First our server hold an application that only serve 4 countries. We had a repeated ddos from bonnet so would like to block all traffic except for the 4 countries that the application serve. the idea ...
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1answer
32 views

How to tell if the server was down because of DDoS of another reason?

my server was down for a couple of hours during the night. i see in the cpu load monitoring in the amazon AWS console that it was 100% load. also, the network in jumped (but no that dramatically) so ...
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0answers
785 views

postfix queue active and mail transport unavailable

I am not very familiar with postfix, but I am pretty sure that what I am seeing in my logs is not a good thing, and I was hoping someone here might be able to shed some light on what is going on and ...
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2answers
78 views

Will MX records with a longer TTL help mitigate effects of DoS attack?

We have our email hosted at Google Apps, and have our DNS servers for the domain setup at Namecheap. About a month ago our website went down (not a big deal, since it's most just a contact info ...
1
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1answer
54 views

Apache MySQL Server Crashing - Large number of connections from localhost

I'm running a 2GB Centos 5.9 server with the standard LAMP setup. I'm running a wordpress website so it's nothing to demanding performance wise. However the MySQL server seems to keep crashing as I ...
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2answers
1k views

Apache - How to limit Content-Type header length to avoid CVE-2014-0050?

On Thursday a DoS problem with Tomcat was announced in a Tomcat mailing list ("[SECURITY] CVE-2014-0050 Apache Commons FileUpload and Apache Tomcat DoS"). An attacker seems to be able to cause an ...
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5answers
1k views

How can I defend against a DRDoS exploiting NTP server on an ESXi host?

Recently, we had some problems with one of our ESXi servers, caused by the NTP Server DRDoS Amplification Attack using ntpdc. How do I configure the NTP server on ESXi to not be exposed to this DDoS ...
12
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1answer
1k views

What is an open DNS resolver, and how can I protect my server from being misused by hackers?

I don't have the strongest background in computer security, but yesterday one of my company servers was shut down by our host. It's a server assigned a public IP where I host several web-service ...
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1answer
79 views

How to read sFlow?

We currently have a very large outbound DDOS Attack coming from one of our machines which is on a Brocade switch and monitored by PRTG. I am looking at the sFlow v5 8 sensor and see Top Talkers and ...
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0answers
152 views

My Bitnami Tomcat Stack (on EC2 AWS) is generating DoS attack

I have a very small java web app that is deployed on a Bitnami Tomcat Stack on AWS. We are using this app in the company with only 5-10 user base daily, and generating only below 100MB of traffic per ...
0
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1answer
844 views

mod_security configuration issue: Error parsing actions: Unknown action: ver

I am trying to install / configure mod-sec using this tutorial, which uses the OWASP ModSecurity Core Rule Set. However when I go to restart apache, I get the following error: Syntax error on line 53 ...
3
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3answers
411 views

Can't stop DDOS [duplicate]

I need a little help dealing with ddos. I'm experiencing 1gb ddos attack on my server and I don't know how to stop it. (1gbs is the maximum speed of the server.) I've the following iptables rules: ...
0
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1answer
290 views

How to prevent mod_evasive false positives on partial downloads of large files

I am getting a lot of false positives notices sent by mod_evasive installed on my apache servers. They always happen on large PDF file downloads. When clients download PDFs from my site, they use many ...
5
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3answers
2k views

DDOS using ntp server

I've heard about new kind of DDOS where ntp is used for reflection . My questions are really simple : Can you please give details on how they work and clarify? Since ntp is ran over UDP, I suppose ...
1
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1answer
71 views

How to avoid DoS in a proxy environment with 1 IP only

We have lots of servers behind a proxy (nginx) and an IP. Users are reaching to their servers through proxy. We add their domain to proxy and route traffic to their servers. The problem is sometimes ...
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0answers
94 views

sshd running at 100%

I'm running an Ubuntu/WordPress server on Amazon EC2 which is experiencing problems every 24-48 hours: I get a CPU alarm from EC2, log into the server, and discover sshd is running at 99.9% CPU. This ...
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2answers
39 views

Ideas for redundant / geographically optimized web hosting solution

I need to setup a web hosting solution with the following requirements: No single point of failure. Ability to handle reasonable DDOS attacks (non traffic saturation types) Servers located in ...
2
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1answer
2k views

/usr/bin/host being used in HTTP DDoS on Debian? [duplicate]

So I got an abuse complaint for one of my dedicated servers, running Debian 6.0 Sure enough, sometimes, top shows /usr/bin/host using a lot of CPU for no apparent reason, and netstat shows process ...
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4answers
467 views

Can a ddos attack stop me from ssh'ing into my server?

SOLUTION NOTES Wow so many great things to think about. We have installed mod-security and looking into Monit. Plus not that I don't like my boss but he is not an I.T. guy in profession nor hobby so ...
2
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2answers
110 views

How can I mitigate DNS Server outages?

Let's say I have a root domain of "mysite.com". That domain and its sub-domains have DNS served by an external service - let's call them Setwork Nolutions. If this external company is hit with a DDoS ...
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0answers
76 views

Drop in HAproxy traffic with increase in connections

We have an intermittent issue that involves a severe drop in network traffic (both IN and OUT) on our HAProxy load balancer. It happens a couple times a day. HAProxy is configured to limit requests ...
5
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1answer
94 views

How to minimise effect of mischievous, persistent POST requests

For a few months now one of our shared hosting servers has been persistently and constantly hammered by "POST /" requests from what must be hundreds of thousands of individual IPs. On a number of ...
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0answers
136 views

What advantages does mod_evasive have over mod_security2 in terms of DDOS protection?

I'm running an Apache2 server in front of a Tomcat and I need to implement a DDoS protection mechanism on the Apache2 layer. I have two candidates: mod_evasive and mod_security2 with the OWASP core ...
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1answer
39 views

Is there a way on the server side to punish evil visitor? [closed]

For example an admin page that should not be visited unless with special cookie or query string token. The point being that anyone who tried and failed would likely be with bad intention. Or when the ...
0
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0answers
133 views

DDoS attack simulation using MININET

I´m developing some dynamic security policies using SDN, one of them consist in how the network should respond to a DDoS attack detection. So, I would like to test my policies but I'm having some ...
0
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0answers
94 views

server reached MaxClients setting, consider raising the MaxClients setting

this is my mod-status report. Do you think I could be under a DDOS attack? Thanks Current Time: Monday, 14-Oct-2013 18:56:57 CEST Restart Time: Monday, 14-Oct-2013 18:54:48 CEST Parent Server ...
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2answers
372 views

Apache DDOS Prevention

Moved from Stackoverflow. I have a LAMP server running Ubuntu with security programs such as Denyhosts, Fail2ban and with Mod_security installed but seem to constantly be the target of a DDOS attack. ...
0
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1answer
902 views

Recent module, what is preferred rcheck or update?

Let's say I have the following rules: iptables -P INPUT DROP iptables -P FORWARD ACCEPT iptables -P OUTPUT ACCEPT iptables -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT iptables -A ...
0
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1answer
85 views

DDoS Protection [closed]

Let's say I order a half rack (22U) at any colocation company. They give me a GiGe port and I need DDoS protection. If I use a slot in my rack for Arbor protection, will I be protected up to a certain ...
0
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0answers
19 views

Intelligently filtering bogus query strings

A vBulletin site I maintain is on the wrong end of a DoS attack which is inexplicably routing through CloudFlare unimpeded by their DoS protection. The requests look like this: 1 /?ZZZZCQG=XJXAUD ...
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1answer
116 views

DDoS Attacks & Convictions [closed]

I could probably make a better title, edit it if you find a better way of phasing my problem. Basically what's happened is that a gameserver host thinks I keep attacking their dedicated server with a ...