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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Why is it difficult to catch “Anonymous” or “Lulzsec” (groups)?

I'm not security literate, and if I was, I probably wouldn't be asking this question. As a regular tech news follower, I'm really surprised by the outrage of Anonymous (hacker group), but as a ...
48
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5answers
18k views

How do major sites prevent DDoS? [duplicate]

As far as I know, I have never heard of or seen any large scale web sites like Amazon, Microsoft, Apple, Google, or Ebay ever suffer from DDoS. Have you? I have a personal philosophy that the bigger ...
47
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6answers
18k views

What techniques do advanced firewalls use to protect againt DoS/DDoS?

It is hard to protect a server against Denial of Service attacks, DoS/DDoS. The two simple ways I can think of is to use a server with much resources (e.g. CPU and memory), and to build the server ...
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10answers
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DDoS - Impossible to stop?

Is it possible - in theory - to stop1 a DDoS attack of any size? Many people claim it's impossible to stop DDoS attacks and tell me I just shouldn't mess with the wrong people on the internet. But ...
26
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5answers
3k views

DDOS - security or operational risk?

The chief security officer of a medium sized IT company (400-500 employees) recently released a bulletin in which he stated that DDOS attacks are not a security risk but an operational one. Also I was ...
26
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2answers
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How can a Software application defend against DoS or DDoS?

Most of the solutions for DoS attacks are not at the application level. In case I am using a proxy server, what are the possible countermeasures for DoS at the application level?
23
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3answers
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Since I can set the source IP address to anything using raw sockets, does this mean I am untraceable?

For homework, I coded a TCP packet with raw sockets. So I was also able to change the source IP address to whatever I wanted. So why can't someone just make a program, which sends millions of these ...
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3answers
5k views

How do DoS/DDoS work?

In the last days one could frequently read about attacks from anonymous and LulzSec against different platforms like Sony or HBGary etc. Yesterday for example they DDoS'ed soca.gov.uk and jhw.gov.cn. ...
20
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6answers
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Why do DDoS attacks cost a fortune to stop?

I have read so many stories that a major DDoS attack is causing companies thousands of dollars to mitigate. I have two questions: Is this because they try to keep the servers accessible to real site ...
20
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5answers
18k views

How to simulate DDoS attacks from the Internet?

The idea behind security tests is easy. You want to know what a hacker can do - you hire a security expert who acts like a hacker to see how far he can get. You want to know what an evil admin can do ...
18
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3answers
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DNS Amplification DDOS attack

During the weekend I made some tests to simulate an DNS Amplification DDOS attack. sending about 90Mb/s traffic I was able to generate about x.x Gb/s amplified traffic which sent our datacenter ...
17
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2answers
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Web Developer's responsibility for DDoS [closed]

If my website is targeted for a DDoS attack after I have been paid for completing the website, and I get an angry phone call from the client regarding outage of service, what do I do? It hasn't ...
17
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4answers
703 views

Global Blackout is a myth?

In order to shut the Internet down, anonymous claimed that putting-down the 13 root DNS servers of the Internet and therefore disabling the HTTP Internet, the most widely used function of the Web, ...
16
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3answers
2k views

NTP DDoS Attack on Home Servers

After some half-good script kiddies found out about this exploit or DDoS method, they have been doing it like crazy to websites, game servers, and now my home servers which allows me to work on some ...
15
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7answers
1k views

Would it be possible to overload a large part of the internet, and if so then how?

Last week a news article went viral about a Dutch web hosting/data center company that was allegedly using a DNS amplification attack to DDoS an anti-spam company, because they blacklisting the ...
14
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7answers
38k views

How do I know if my computer is being used for a botnet-based DDoS attack?

A botnet is a collection of compromised computers, each of which is known as a 'bot', connected to the Internet. When a computer is compromised by an attacker, there is often code within the ...
14
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2answers
5k views

Reject IP packets with an ICMP error, or just drop them?

Consider an internet-facing host (the outer firewall). What should be done with undesired traffic: just drop it, or send back an ICMP error such as port unreachable? (In Linux terms: iptables -P DROP ...
13
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3answers
3k views

Accessing a site (which is) under a DDoS

Lets say http://www.an-example-site.com is under DDoS attack. Alice, who does not have direct access to the hardware infrastructure, urgently wants some information which can be accessed through the ...
12
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1answer
1k views

How to make a report after a ddos attack? what information do I need to write on the report?

In my company, after a DDOS against a server, my employer asked me to make an analysis of the attack and to write down some stuff. What do you think I need to write down in my report? Is there any ...
11
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5answers
5k views

What is a DoS Attack and how does it differ from a DDoS attack?

Can some one explain to me the concept of Dos Attacks for web applications ? Also what is the distinction between Dos and Distributed Dos ( ie DDos) attacks ? Wikipedia says : In computing, a ...
11
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4answers
7k views

Looking for botnet IP address feeds to protect against DDoS

I would like to get a live feed of botnet IP addresses delivered from a service and block them under certain conditions. Preferably community based/open source but open to looking at worthy commercial ...
11
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2answers
2k views

How to test against DDoS in a controlled enviroment?

Can you suggest me methods or tools that can help in simulating a DDoS attack in a controlled enviroment (like my private lab)?
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2answers
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Understanding Layer 7 DoS

I recently read this article about how a lone hacker (The Jester) conducts, amongst various other things, his DoS attacks over layer 7 instead of layer 4. It also mentions at one point he was able to ...
10
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3answers
506 views

External websites in logs [duplicate]

I have a website, let's call it www.good.com. I've been getting a lot of requests to www.good.com under completely different URLs than www.good.com. I suspect this traffic is also causing some site ...
10
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1answer
2k views

Effects of DDoS attacks on memory use under Linux

Can someone whose Linux system is under DDoS attacks give me exact data on the effects of the Low Orbit Ion Cannon (LOIC), the High Orbit Ion Cannon (HOIC), Slowloris, PyLoris, Hping etc. on memory ...
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4answers
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mitigating anonymous DOS (tor combined with pyloris)

I found this rather scary video in youtube, that takes DOS to a whole new level, by making it look like coming from multiple sources. As a counter measure to Rsnake (Robert Hansen) slowloris.py ...
8
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4answers
4k views

Block all BotNets and TOR addresses from accessing our site

I've heard that many DOS attacks and general "black hat hacking" attempts occur over the TOR network. Is it possible for me to dynamically block source IP's by their presence in a BotNet or similar ...
8
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3answers
22k views

How can I identify open DNS resolvers in my network?

This article highlights how open DNS resolvers are being used to create DDOS attacks across the internet. How can I identify whether any of our DNS servers are open? If I find that we are running ...
8
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1answer
548 views

How is DDoS possible if you're not listening to the DoS traffic?

I've read about DDoS attacks and specially the amplification techniques. For example, the DNS amplification technique where you can send queries to open resolvers pretending to be the victim, then [if ...
8
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5answers
12k views

How to trace a DDOS attack on a dedicated server and block it?

I have a dedicated server and I'm hosting a game, and the web page (using Apache) for account registering. The server is being ddosed since 8 months ago till today. I've tried to talk with the server ...
7
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5answers
2k views

How does CAPTCHA mitigate DDoS attacks?

This seems like an easy question, but I've failed to find an answer. One of the uses of CAPTCHA is to cope mitigate Denial of Service attacks. Suppose an adversary performs excessive login attempts, ...
7
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6answers
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how to mitigate a DDoS from botnet on your website that comes from random IPs

I am wondering how do you mitigate a ddos attack which is coming from a botnet and hitting random URLs on a website. If there was a consistent URL it was hitting then it would be fairly simple, and ...
7
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3answers
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Why is it so hard to trace origins of DDOS attacks?

According to the July 2009 cyber attacks Wikipedia article, US & South Korean governments suffered a DDOS attack on their websites. However, up till now they have not been able to find any ...
7
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4answers
4k views

Can someone launch a DOS attack on my IP

Suppose, I have a static IP on my PC and is known to others. None of my softwares listen for remote connection. Is it still possible for someone to DOS attack me in such cases? If yes, how it is ...
6
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5answers
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I have a client that is worried about DDOS attacks on their site, and they want penetration testing. Will that help?

My client wants to look into hiring a third party to perform penetration tests on the website that we're developing for them. The website is just a simple 3-month contest site where people can upload ...
6
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3answers
2k views

First steps in preventing DOS attacks

My server is currently being attacked from another server. This is my log: root@my-server:/var/log# tail -f auth.log Feb 19 11:53:08 my-server sshd[3745]: Disconnecting: Too many authentication ...
6
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3answers
648 views

Can the IPS technology in a UTM prevent a DDoS attack?

Does a Unified Threat Management appliance (UTM) with Intrusion Prevention (IPS) enabled have the ability to prevent a DDoS attack? I have read some articles and none of them have a perfect ...
6
votes
4answers
931 views

How is a ddos simulation any different from a real attack?

I asked a question earlier today on serverfault, but found out that there was also a security stack exchange. I had conflicting answers from there. The following is the link: ...
6
votes
1answer
206 views

Parabolic Denial Of Service — Would it work?

Would this DoS attack be effective: Attacker determines target (10.0.0.1) Attacker sends ack packets to a buch of web servers with a src addr of 10.0.0.1 Servers reply to 10.0.0.1 with syn packets ...
6
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1answer
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High concentration of UDP traffic, good or bad?

Should a network have a high concentration of UDP traffic compared to TCP traffic bad for a network especially in the context of network security? I'm looking at my organization's network protocol ...
6
votes
3answers
707 views

Lessen impact of DoS attack on cpu-expensive login?

This is a follow-up to my previous question: Prevent DOS against RSA authentication. This question is also discusses a similar problem: Prevent denial of service attacks against slow hashing ...
6
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4answers
781 views

Secure authentication: partial client-side key stretching… please review/criticize my idea

I am trying to figure out what would be the 'perfect' authentication system for a website. On one end, we know that simple hashing algorithms can be brute-forced or cracked in other ways. Hence why ...
5
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5answers
2k views

SYN Flooding issue

I recently purchased a server with "DDoS protection" and a 1gbps uplink. What I can't figure out, is that I'm suffering from SYN floods. Isn't the large amount of bandwidth available to me supposed ...
5
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3answers
2k views

How are server overload and DoS/DDos different?

I know that server overloads are caused due to excessive number of genuine requests and DoS due to malicious request. But, my question is, if you have designed a system for Overload mitigation, does ...
5
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6answers
7k views

Why can we not block DNS Amplification attack by blocking UDP packets or DNS response packet?

I mean if the attacker tries to ask all the open DNS resolver respond to a web server. The web server can just block its UDP ports. If the all the DNS response go to a Authoritative ...
5
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2answers
3k views

Does a DDoS attack have other purposes beyond a lack of availability? [duplicate]

I'm currently researching DDoS attacks for an article I'm writing and apart from the obvious lack of availability of the target host and their services, is there anything else a DDoS can help ...
5
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2answers
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How can I detect/withstand DNS amplification attack?

I am a developer, and I am trying to get an insight into what could I do to enable my application to withstand a DNS amplification kind of attacks. Would such prevention methods help against DOS type ...
5
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2answers
2k views

How could a SYN flood affect a home router

I was curious how a DoS attack would affect a home router. In particular, I'm interested in how a SYN flood would affect a home router. The reason I'm interested is due to a Cisco document I read. ...
5
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1answer
2k views

Can you be DDoS'ed even if you are behind a home router with no open ports?

I was wondering if someone can become a victim of a DDoS attack as home user when only his IP is known by the attackers but he is behind a router with no open ports or other known vulnerabilities? ...
5
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3answers
432 views

DoS by consuming all hosting trafic

Given a small website hosted on a small data plan, is it possible for someone to keep doing requesting for my website URL or just an image hosted on my website that will consume all my permitted ...