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Questions tagged [ddos]

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.

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.

For information on what to do about a DDoS attack that is underway, see How can I stop a currently active DDoS attack?

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Stop DoS attacks with an IP tables rule?

I was wondering if I could prevent small (D)DoS attacks with a simple IP tables rule? By small I mean that they are flooding my web server with about 400+ requests from one or two IP addresses. I can drop the IP addresses after I notice that they…
Josh Foskett
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DDOS attack - How to prevent

Recently I read about Denial of Service attack on Amazon & PayPal. I am curious that how this is performed. These big companies must have huge servers, so DOS would require billions of bots to access it. So my questions are How DDOS attack…
ashmish2
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DDoS Protection Services - are they good enough?

first of all, I understand that it's better to have DDoS protections on data center level. But our DC is not ready to provide good quality of protection. So we thinking about using some external DDoS protections service. I have googled several,…
Tonik
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Snort rules for syn flood / ddos?

Can someone provide me rules to detect following attack : hping3 -S -p 80 --flood --rand-source [target] I'm having problem with rules since packet comes from random source. My current rules is : alert tcp !$HOME_NET any -> $HOME_NET 80 (flags:…
NoodleX
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DDoS and Heroku

I use Heroku as my hosting solution. So, if some bad man attacks my site with DDoS, what should I do?
Yuri
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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 attack? Or, if I switch off the service, will…
fefe
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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 there must be some kind of forged packet…
user130370
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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 occasions this has overwhelmed the server and led to…
Richard Maynard
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Correct way to handle security threats to web server on budget

During our annual security review I was reminded of an incident earlier this year where we received a threat to our organizations web server. It was over a organization policy and threatened to DDoS our site. Fortunately, nothing bad came of it and…
lswim
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How can I block a specific type of DDoS attack?

My site is being attacked and is using up all the RAM. I looked at the Apache logs and every malicious hit seems to simply be a POST request on /, which is never required by a normal user. So I thought and wondered if there's any sort of solution or…
Mark
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Web site kills hard disk I/O, how to prevent?

The situation: I have a server, on which we have 2-3 projects. Starting not long ago, the server started hanging up (We could not connect to it by ssh, and the connected clients had to wait 20 minutes for top to give results) Early today I managed…
Taras Voinarovskyi
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DDoS attack case study - Korean election watchdog's site

Is it possible to break only some of a web site services using DDoS? For example, disabling only the search feature of a specific website. I raise this question following a controversy in South Korea, where part of the election watchdog's web site…
Wonil
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How to block null/blank user-agents in IIS 7.5

We are going through a large scale DDOS attack, but it isn't the typical bot-net that our Cisco Guard can handle, it is a BitTorrent attack. This is new to me, so I am unsure how to stop it. Here are the stats IIS is processing between 40 and 100…
Jeremy Boyd
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100mb/s upgrade to 1gbps network - To Prevent DDOS

I have been under constant DDOS attack the last couple of weeks. Now it seems my servers network is being flooded till it just doesn't have space anymore to receive and send normal packages. I run CENTOS 5.6, and i have hardened SYSCTL and iptables…
Mr.Boon
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Mitigate DDoS attack with HAProxy

We were targeted earlier today by a DDoS attack. There was 20x as many connections as normal on our load balancer (HAProxy), and all the backend nodes continued to go down during this attack. System structure: HAProxy > Squid > Apache (for…
Matt Beckman
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