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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How can node addition/substraction be done while keeping randomnes in their connections in a P2P unstructured network?

If a unstructured P2P network that uses an admission mechanism for new peers entrance gets completely offline because of a massive attack (e.g. massive DDoS), after reconnecting, peers will try to ...
5
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2answers
119 views

How do I understand my CPU usage on a DNS server?

I have read and understood Can you help me with my capacity planning?, but I'm not sure I understand what my next steps are in a DNS server scenario. I think my CPU loads are high or that I might be ...
3
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7answers
643 views

DDOS Attack Victim - How much to Admit?

Here's the environment: Website that hosts a forum/journal/bboard/email/socialmedia application in walled garden (ie you pay to get to use it or are invited to do so Many Clients pay to use the site ...
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0answers
9 views

slow post attack mitigation breaks slow file uploads

To mitigate against slow post attacks, I set the following in my apache. RequestReadTimeout header=5-20,MinRate=500 body=10-60,MinRate=500 The problem with this is when users are uploading files on ...
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1answer
849 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 ...
2
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2answers
223 views

Monitor DoS attack with snmp [closed]

Is there any way to monitor DoS attacks with SNMP or any other software which based on Linux and could monitor router / switches and alert when a DoS attack is observed?
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1answer
3k views

Iptables ratelimit UDP DOS attacks [duplicate]

Well, I've been a victim of Ddos attacks and I really can't figure out how to avoid it. On some machines it works, while on some it doesn't or probably I'm doing it wrong in some way, Attackers are ...
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2answers
542 views

Prevent scanning of the Apache's /default directory [duplicate]

I have two directories, under /var/www/vhosts: mydomain/ and default/. Files in default directory can be accessed using IP address of our server. I have checked Apache log and somebody is ...
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1answer
1k views

Best Practice for captcha based protection against D.O.S to Nginx Proxy [duplicate]

The idea is explained here In simple words, Nginx Proxy plays the role of load balance and transmits the HTTP/HTTPS requests to servers. If the number of request times within a certain period from ...
2
votes
1answer
151 views

How can I implement an ip whitelist to protect my server? [duplicate]

I'm going to start running a gameserver soon and I want a way to reduce the the damage of a denial of service attack. I want to make it so when someone joins the game their ip adress is added to a ...
4
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1answer
223 views

Windows server 2008, a very small DDoS is able to kill my server [duplicate]

So I have this i7 3.2Ghz 6-core dedicated server running Windows Server 2008, with a 1Gbps internet speed. Everything runs fine and nice, and the machine is strong enough to handle even up to 700 ...
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1answer
173 views

Is this DoS attack [duplicate]

I am seeing a huge number of connections from a single IP. # netstat -alpn | grep :80 | grep 92.98.64.103 tcp 0 0 my.ip.address.x:80 92.98.64.103:45629 TIME_WAIT - ...
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1answer
181 views

iptables connection limit does not work on debian [duplicate]

I'm trying to set up some basic DOS protection. The following iptables rule works on a CentOS box but NOT on debian (wheezy). #limit the parallel http requests to 50 per class C sized network ...
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votes
0answers
5 views

What is the optimal (best) value for PORTFLOOD in CSF firewall? [duplicate]

What is the optimal value or best value for PORTFLOOD in CSF firewall. This setting is for shared hosting environment, where we have hosted 100s of small websites. Mainly we want to prevent it from ...
0
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2answers
294 views

netfilter ip_conntrack and (d)DoS [duplicate]

Does using netfilter.ip_conntrack in the kernel in anyway help mitigate (d)DoS attacks or does it make it worse? I know it adds the ability to track connections and such but just curious if it helps ...
1
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2answers
323 views

PHP web hosting: how to prevent clients to DOS/DDOS? [duplicate]

I'm providing a partial web hosting solution where my clients may upload and execute their own php scripts. Besides the security routine I'll have to check (off topic here) I would like to know ...
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votes
1answer
371 views

TCP DOS: How to terminate CLOSE_WAIT connections? [duplicate]

One of my servers is getting DOS'ed - there are a large number of connections in the CLOSE_WAIT state which are preventing legitimate users from connecting to the system. So is there any way to close ...
4
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2answers
102 views

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

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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2answers
216 views

blocking udp attack ip with iptables [duplicate]

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
14 views

What is a typical request rate per hour in a distributed attack?

I am concerned that some static files hosted publicly in S3 can be the target of an attack that aims to hurt me financially (ramping up my AWS bills). I have set up a logging system, that runs every ...
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0answers
37 views

We're getting a lot of strange requests to our server [duplicate]

we recently started getting a lot of strange requests to our server, and it can't handle it. Some examples from our access log: 120.198.243.34 - - [16/Feb/2015:10:26:02 +0100] "GET ...
4
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3answers
385 views

I know how to scale my software, but how to prevent downtime because of network outages? [duplicate]

We are running rather large LAMP sites which scale well software wise. We use redundant load balancers in front of a bunch of webservers using MySQL via a proxy in master-slave-slave-slave. We are ...
0
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3answers
341 views

DDoS Network Protection Devices

In our office we're running a Cisco ASA 5510 firewall. Is this device enough if we want to protect against DDoS attacks? What devices (like cisco guard, etc) do you recommend and what's the user ...
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1answer
26 views

Email Virus initiating a DOS Attack [duplicate]

I have a VPS that keeps getting shut down because of excessive inbound or outbound traffic. I thought I had a virus on my server and with it shut down so was my email server. So I got a new VPS ...
2
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4answers
998 views

Does a VPS mitigate risks of a DDOS attack versus shared hosting?

A client of mine has a website on a shared hosting account, and one of the other accounts on that server was targeted by a DDOS attack, which of course brought all of the websites on that server down. ...
2
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1answer
31 views

IIS network scanner protection

Is there any software tool for a Windows Server (with IIS installed), where I could set up "rules" to block incoming HTTP requests with suspicious behavior? Like, say, if someone starts scanning my ...
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3answers
154 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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2answers
135 views

My servers are overloaded with random GET requests. Why? [duplicate]

I'm getting a huge amount of traffic to web servers looking for bittorrent type queries: 110.152.78.14 - - [27/Jan/2015:01:45:22 +0000] "GET ...
13
votes
2answers
1k views

Has anyone got billed for malicious activities (DDoS) on a cloud server? [closed]

I would like to know if anyone got billed beyond expectation on a cloud service because of malicious activities (DDoS, etc)? How does EC2 and/or Rackspace Cloud handle these issues? Thank you!
0
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1answer
40 views

Mitigate DDos on Windows box [duplicate]

I would love to know, If you know some way to mitigate DDos/Dos attacks on Windows. In Linux we can Mitigate using the IPTables Almighty, but I wonder If there is something like that in Windows. I am ...
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votes
1answer
183 views

What are some acceptable easy solutions against DDOS? [duplicate]

IIRC the best way is to set up a firewall. But what are some easy solutions that doesnt require a lot of knowledge? I use nginx (but i hope the solution can be applied to lighttpd). Would changing ...
0
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1answer
36 views

Content Redirection Attack on a Server

I'm working with an apache 2.2 server that is receiving lots of requests for content that does not exist on the server (edit: the specific content request changes frequently). It appears to be an ...
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0answers
578 views

High outbound network traffic on Tomcat under process nodeJR [duplicate]

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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3answers
1k views

What “Syn Proxy Servers” are recommended? Or how to build one?

My questions are: 1.) What is a recommended "SYN PROXY SERVER" to filter bogus SYN Attacks and only forward "handshaked" valid connections to the host behind it (to be protected). I search the term, ...
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1answer
39 views

Are Google Apps implicitly DDoS protected?

Especially when talking about Google's Project Shield, people refer to an "internal anti-DDoS infrastructure". I could not find any more detailed information on such thing, and if it spans all the ...
0
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0answers
27 views

Suddenly many requests to /announce on server [duplicate]

We currently receive a lot of unusual requests on our Apache2 web server which impair the server's performance. Most requests go to /announce and /announce.php. Both addresses do not exist - 404. Here ...
0
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0answers
101 views

Using an Ubuntu VPS as a firewall/router

I have a dedicated server running ubuntu 12.04 hosting several websites and other applications which require client IP's to be visible, however the main dedicated server does not have DDoS protection, ...
0
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1answer
117 views

How to AVOID getting caught in a DDOS meant for someone else (not prevent)?

So we have a load balancer and all that jazz set up with Rackspace. However, guess what, our clients' websites were down again today. It seems that Rackspace should have their load-balancer ...
1
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2answers
182 views

Setup alternative DNS entry while DNSimple is down for DDoS?

Have an app on Heroku with domains registered with DNSimple. DNSimple is undergoing DDoS for hours. (Sharing the naked heroku URLs with users is almost workable, but not an option as the OAuth ...
0
votes
1answer
118 views

How can I block traffic FROM Amazon Technologies Inc. (possible DDOS attack) [closed]

I've a small website (portfolio) and I usually notice traffic of about 10-20MB per day. But for few recent days I've noticed about 10-15GB (1000 times more) each day for 4 days now (and it continue ...
1
vote
0answers
30 views

Multiple pearl processess all hitting one IP address DDOS source hack? [duplicate]

I have been running at high CPU loads 45 45 45 ish for a while, updated cpanel / apache so far but tracing PID's that are running I find the following all with the same IP.. [code] select(8, [3], ...
0
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0answers
89 views

My VPS send an outbound attack

My VPS was sending an large outbound attack 10MB/s. It's normal max 300Kb/s I've tried searching around the internet, look for some /tmp folder, installed Linux Malware Detect, installed csf with ...
0
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0answers
54 views

How to redirect to an other link when excess request (limit_req) with Nginx

I have been trying to limit the requests coming from a single IP address successful with module limit_req in Nginx. But now I want to redirect to an other web-page for showing some messages.How could ...
0
votes
1answer
73 views

How to drop first udp packet from a source with iptables?

As a defense against distributed udp flood, I need to drop first udp packet from a source and accept other than first packet. Does iptables has capability of doing this? If yes, how?
24
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6answers
27k views

How can I prevent a DDOS attack on Amazon EC2?

One of the servers I use is hosted on the Amazon EC2 cloud. Every few months we appear to have a DDOS attack on this sever. This slows the server down incredibly. After around 30 minutes, and ...
0
votes
1answer
139 views

GRE Tunnel in CentOS

How to create a GRE Tunnel in CentOS pointing all connections to server A for the server B? I have a public server with DDoS protection and need to use this as a firewall to filter acess to the other ...
0
votes
2answers
41 views

What is the benefit of cloudfares or inkapsulas etc ddos protection [closed]

My Server get even more attacked via DDOS. And im thinking about buying a service like cloudfare or incapsule for preventing DDOS. But i dont understand one thing. When the attackers see that the ...
1
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2answers
214 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 ...
0
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1answer
100 views

Can I block inbound traffic from a certain ISP

The problem My server keeps getting DDoS attacks from IP's belonging to Ecatel in The Netherlands. I wrote them a month ago and still haven't heard anything, and keep blocking individual IP addresses ...
0
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2answers
2k 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 ...