Distributed Denial Of Service (DDOS) is the intentional paralyzing of a computer network by flooding it with data sent simultaneously from many individual computers (so-called zombies) which are used to stage DDOS attacks

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How will IPv6 affect DDoS mitigation techniques?

IPv6 introduces a much larger address space than IPv4 and with it there are many new techniques in creating and mitigating DDoS attacks. What are some examples of risks and mitigations? For example, ...
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Using SYN cookies to perform a DOS attack

In my software security class, we had this question: You are the system administrator for a provider that owns a large network (e.g., at least 64,000 IP addresses). Show how you can use SYN ...
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My server is used for DDoS attacks

I have webserver (centos + cpanel), and one of the clients used my server for DDoS-ing, how can I identify that client/user? What logs should I look to, is there any settings I can modify so such ...
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Where is the limit between an attacker and a victim (zombie) in a DDoS attack

Let's say that A is DDoSing B and I'm a member of his botnet. Who says that I'm not a real attacker but a victim? How you determine it?
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what is a good public available iptables script for ddos mitigation?

what is a good public available iptables script for ddos mitigation?
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How does a Distributed Denial Of Service Attack work

Let's assume that a hacker has already infected an X number of PCs , each one of them is online. How will he actually perform this attack? Just send ping requests or use his very precious tool to do ...
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Creating a DDoS attack using DirectConnect

I have been trying to hack around with Apex DirectConnect. What I wish to do is to utilize the querying nature of P2P apps like DC to generate a DDoS attack (see links for reference here, here and ...
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Are voluntary / manual DDoS illegal?

Since DDoS is simply a group of subjects coming together to send requests to a particular server, is it true to say that a voluntary DDoS is perfectly valid and legal in US? By that, I mean that a ...
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Could Stock Exchange be shut down by HFT attack vector?

First of all, stock, not stack exchange. I just read this post on Krypt3ia. In short, it says that HFT attack vector in combination with DDoS is possible new nemesis for stock exchange IT systems. ...
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Find out how my server is being used for DDOS attacks

I got an email from Amazon that my Amazon EC2 server is being used for DDoS attacks and they have closed all ports except SSH. This is tragical for me but I have not been able to find out how and ...
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unknown MAC address in the LAN, DD-WRT router

I am using a linksys router with DD-WRT firmware with a WiBro internet connection, the ISP uses a hub with multiple user connected to it. The issue is that an unidentified MAC address seems to pop up ...
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How similar are bots regarding their HTTP GET request?

Lets assume a botnet is attacking a website by HTTP GET flooding. To find the bots, the only way seems to be finding the similarities of the HTTP GET requests considering the URL and header fields, ...
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Blocking incoming traffic from privileged port (< 1024) to mitigate DNS DDos Amplification attacks

Hope someone can clarify. As I understand, in a DNS DDos Amplification attacks Multiple DNS queries are sent to a vulnerable name server with the source IP spoofed to that of the target server. The ...
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How web application firewalls protect application from DDoS attacks?

How to protect a web application from DDoS by the implementation of Web Application firewalls? How effective is this method?
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DDoS Protection for DNS providers

Zerigo, our DNS provider has reported to have been under heavy DDOS attack in the last 24 hours or so. Considering the distributed nature of DNS, and their architecture consisting of 5 main DNS ...
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Spider Attack from several search engines at once

Hello my server is getting hit by spiders from bingbot, google, yahoo, yandex, and some place in the UK all at the same time crashing it. While I have no reason to think any one person did this, it ...
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what is the Akamai Name Server i see at some big companies

I have played with DNS a lot lately, and i have found that some big companies's web sites uses the Akamai NS as the Name Server for thier WWW servers, for example: $>nslookup > www.redhat.com ...
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Can an attacker slow down my server without compromising it?

We have a Linux server with WHM/cPanel which has been running without problems for almost 3 years now. Yesterday, the server became unresponsive (it was definitely there though) for around an hour. ...
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Will a DDOS attack prevent outbound traffic?

Imagine a scenario where there is a DDOS attack against a target - clients would be unable to connect to the target, but I would like to know if the target could initiate a connection to the outside, ...
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How to detect bots clicking a link?

I own a url shortening service. I want to deliver only legitimate statistics to my clients. There are possible scenarios that a particular user writes a script to automatically open the shortened URL, ...
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Stopping DDOS TCP SYN and UDP flood attacks

I would like to know if it's possible to stop a TCP SYN OR ICMP Flood attacks if these attacks are detected at time. What is the most accurate process to filter these addresses if the only way is to ...
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DDoS on LAN: How to Defend?

DDos on a wired network has to be extremely rare, since the intruder has to be physically connected to the network. However, let's say that it still managed to happen. How would you be able to defend ...
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How to mitigate SSL based DDoS attacks?

as you probably know the problem with SSL based DDoS attacks is, that the traffic cannot be analysed and filtered by a DDoS mitigation service provider such as Prolexic, Akamai, Radware, etc. without ...
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IPTables DDoS protection working with per client IP address counter AND UDP

I am looking to protect LAMP server with a software, which will detect above average number of requests from single IP numbers (in this case DNS queries), and add these hosts to IPTables deny chain. ...
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771 views

Strange Apache access logs

A site of ours has been targeted by some kind of strange attack and I am trying to work out exactly how it has happening. Basically, the strangest thing is that the logs seem to correspond to entirely ...
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Which IP / Client is being Ddosed?

I currently have some Vps's and shared hosting plans with a few hosting providers. Recently one of my shared hosting accounts was suspended due to a denial of service attack. I understood why they had ...
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Protection against DDoS when using proxies

We're trying to protect some sites that are primarily located in Asia using distributed caching. These sites commonly come under DDOS attacks. We are using fail2ban, but still have two problems: ...
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Downloading operating systems vulnerable to TCP amplification

I am doing a security research project on TCP amplification, and was looking to download vulnerable OS's for testing. From what I have researched mostly ancient linux kernels (2.0.x and below) and ...
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Distributed Denial Of Service Attack Mitigation

Is there any way in which you can stop a DDoS attack(or any measure that you can take), if the packets sent by the attacker look like normal traffic? I got the question on an interview (how would you ...
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Outbound DDOS attack from a centos 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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What is Open Resolver Project and how does it solve DNS reflection attacks?

What is Open Resolver Project and how does it give a solution for DNS reflection attack? I also read that Open Resolver Project follows BCP38. What is BCP38?
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Denial of Service on SSL services

When the SSL handshake takes place, is there a point where the computational work done by the client is significantly less than the computational work done by the server? Could such an imbalance be ...
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Is opening a new mysql connection for each query potentially unsafe?

I am doing some unit testing and noticed that if I click (or have multiple people clicking) the same filter very very fast (very precise I know;) eventually I get a "The connection is already open." ...
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Lots of failed outgoing sshd attempts. Am I hacked?

For the last two days I've been seeing lots of lines in my /var/log/auth.log that look like: sshd[xxxxx]: error: connect_to 0.gravatar.com port 80: failed sshd[xxxxx]: error: connect_to ...
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What approach would you choose to defend againt DDoS attacks from Nginx level?

I use Nginx compiled with the Naxsi module to protect against some vulnerabilities (SQL injection and cross-site scripting). Now I need to apply a layer of poor man's DDoS protection at this level. I ...
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Why is it easy to detect network layer DDoS attacks?

I have seen numerous research papers that claim it is "easy to detect network layer DDoS attacks" without saying why. Usually these research papers focus on detection or prevention of application ...
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129 views

Types of attacks outside of AppSec and Vendor-Specific Systems?

I'm reading up on the OWASP Top 10 for helping me defend my web app against common "app sec"-type attacks (SQL Injection, CSRF, etc.). And in a recent question I was prompted to not only use OWASP Top ...
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How should I configure a Citrix Netscaler to protect against HTTP, TCP, or UDP flood attacks?

I have a Citrix Netscaler and want to configure the appliance appropriately so that it can protect my hosts from a DDOS. Is this something I can do here, or must I take action on the host itself?
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What is this attacker trying to accomplish?

My client is who is running a recent version of vBulletin is getting lots strange activity and I'm at a loss to explain what the attacker is trying to accomplish. The attacker registers a fake user ...
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cisco asa syn flood detection and response not working

I have a Cisco ASA 5510 (ASA Version 8.3(2)) that has been getting a syn flood attack on it (or more accurately through it - targeting a host behind it) a couple of times a day for the past few days. ...
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Ubuntu server seems compromised for a DDOS attack [duplicate]

So i have this VPS Ubuntu v12.04 Server running with DigitalOcean. Zpanel/Apache/PHP stack was installed on the Server For the past few days it was occasionally down. Initially, I didn't know what ...
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DoS stress test not working [closed]

First off I'd like to say this is my first post on StackExchange, so please let me know if there's anything wrong with it. Also, I don't know much about networking and I'm just making a simple java ...
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Snort Parallelization Techniques and its effect on DDOS detection capability [closed]

I want to ask a query about snort parallelization. 1) Can snort detection rate remains same for all attacks after parallelisation? 2) As the parallelisation of netowrk traffic in each core is based ...
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How to send GET/POST requests without header and agent information

I want to test our DOS prevention system against http requests that are not have header and agent information. Is there any tool I can do that. I tried siege with this command siege -c 3 -b -H ...
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What can a zombie computer feasibly install and run?

I'm experimenting with a Proof of Work system that tries to force the use of a browser in order to solve the client puzzle. Basically, instead of just handing off the puzzle as hash with a well known ...
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DDoS — null route everything not approved

Is it possible to create a route on your internet router which routes traffic unknown to null. So you basically dont even let traffic route into your firewall unless its approved? Can this help detour ...
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How much does it cost to protect your website against DDOS, by tier?

Cross-posted to Quora Today several financial institutes in Israel (banks, stock exchange) were DDOSed. They decided to block all foreign IPs as a first aid measure. While I agree that it was ...
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unprivileged or privileged malware for botnets

For those malwares which are used to organize botnets to DDOS a website, they just need to send and receive HTTP packets. Do they need to be privileged? If they dont need to be privileged, is it true ...
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How is DDoS different from DRDoS?

I understand DDoS is a DoS assault from multiple sources, where a coordinated stream of requests is launched against a target. How is DRDoS different?
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Botnet Attempting to Login to Website

Our server has recently become a target of what appears to be a botnet attack. The first indication was an insane amount of traffic to one of our client's websites - so heavy that the server entirely ...