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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Block connection through proxy in firewall [duplicate]

I'm getting some 'ddos' on my Linux machine (ubuntu 14.04 64bit). I have a lot of connections from IP which are proxy IP's (like tor), on specific port. Question: How to block all proxy connections ...
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12 views

Do websites maintain partial functionality during ddos-like high levels of traffic? [on hold]

I asked this on stackexchange but was told to post here. Forgive me for any technical shortcomings I might have, I have some degree of knowledge of computer science but not extensive. So I'm into ...
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0answers
30 views

Redirect IP to another IP [on hold]

My domain redirects to my Teamspeak 3 Server on port 9987, and it works perfectly. But now I will add a second server to block DDoS so I must redirect my domain to server #1 and server #1 must ...
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2answers
43 views

High inbound and outbound network traffic

Over the last day or so, one of instances has had a large amount of bandwidth consumed. This means that we have nearly exceeded our allowance (roughly the same amount inbound and outbound). Looking ...
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1answer
29 views

Linux DDOS Protection / Gateway without NAT

I need help to configure a box for DDOS protection and provide external ip addresses to "internal" (which aren't really internal) servers. I have 32 IP addresses from my ISP. I want to configure a ...
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0answers
26 views

Use extra firewall to filter WAN traffic before reaching UTM?

I am running a simple web server behind UTM, only port 80,443 is open. However almost 80% of the traffic coming through WAN is trouble. Mostly are port scanners / sniffers or systematically querying ...
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1answer
44 views

Blocking ddos string with iptables [duplicate]

I want to ask how do block spefic packet payload? 14:46:35.837759 IP 145.92.16.14.27017 > x.27030: UDP, length 25 0x0000: 4500 0035 44a4 0000 ee11 53ae 915c 100e E..5D.....S..\.. ...
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0answers
67 views

Exim SMTP reverse proxy

This is my first post on Serverfault, so if I make some mistakes, please let me know. The issue that I'm dealing with right now is a DDoS attack on my Exim mailserver (cPanel) on port 25. From what I ...
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2answers
51 views

How to secure Windows Server 2012 R2 against “open recursive resolver” attack

I received an email from an ISP stating that our server had participated in a DDOS attack against one of their servers--and that we appear to be running an "open recursive resolver". The IP address ...
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35 views

better alternative for tcp_syncookies in linux

In an effort to prevent DDOS attacks I followed suggestions to leave /proc/sys/net/ipv4/tcp_syncookies value set to 1 in my linux box to enable TCP syncookies. However, when I look at this URL: ...
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1answer
53 views

DDOS prevention/mitigation on Linux CentOs server using IP tables

One of our servers has generated a 19Gb access.log in the space of about 24 hours and the server went down in this time. We'd like to implement some measures to safeguard against DDOS attacks but ...
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53 views

mod_evasive can't be installed: “undefined symbol: evasive24_module”

I wanted to protect my Apache/2.4.6 (CentOS) server in CentoOS 7 from DDOS attacks so after searching for some alternatives I found this page. They go through the installation of the modules evasive ...
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0answers
33 views

limit_req on nginx not working

Iam using Ubuntu server 14.04 with apache + nginx proxy over it. I tried to set up limit_req in /etc/nginx-sp/nginx-sp.conf as this: http { limit_req_zone $binary_remote_addr zone=one:1m ...
0
votes
1answer
115 views

Mod_evasive not blocking a DOS attack using HEAD requests

Using Apache/2.2.15 on RHEL6 with mod_evasive config: DOSHashTableSize 3097 DOSPageCount 14 DOSPageInterval 2 DOSSiteCount 70 DOSSiteInterval 1 DOSBlockingPeriod 60 ...
2
votes
1answer
72 views

Protecting against a DOS attack

Someone is DOSing my server. It is not a DDOS attack as there is only one server involved in this attack. I simply put following iptable rule to drop all the packets coming from the attacker: ...
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votes
2answers
63 views

block or log IPs that direct access my website (ubuntu , nginx)

The website is under DDOS, the cloud service is doing a pretty good job for a cost of dozen bugs a month. We are happy! However the attackers have been hitting our site with IP. Currently, we 301 ...
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1answer
124 views

How to stop small DDOS attacks (443 port)?

On the server goes DDoS attack. ~# netstat -n -p | awk '{print $5}'|awk -F: '{print $1}' | sort -n | uniq -c | sort -nr | head -n10 48 109.229.9.53 47 31.207.244.130 45 87.252.227.83 ...
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1answer
43 views

How to prevent password bruteforce in web application? [closed]

I have php web application (nginx+php-fpm). And someone try to bruteforce password. He have a lot of IPs. Also these bruteforce works like DDOS because each time web application starts and try to ...
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39 views

Filtering KVM guests with IPtables

My partner has a server with OVH that receives a constant variety of ddos attacks, while still staying up. We want to use IPtables on the host to filter the guests VM's traffic. The guest VM we want ...
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votes
1answer
77 views

Too large 127.0.0.1 connections with nginx - apache2 [duplicate]

I use nginx as proxy-server apache2 and I have a problem with netstat output: $ netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n 5 109.195.36.169 6 109.195.33.205 8 ...
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2answers
139 views

iptables not blocking IP addresses

I am experiencing DDOS attack on my server. I found out that someone was trying hard on one of Wordpress websites. I disabled that virtual host for temporarily. I am now trying to block their IP ...
2
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0answers
88 views

Stop senseless mass-queries on DNS-server [duplicate]

I have a disturbing problem for a few weeks now ... One of my three DNS-servers (running bind9 as slave of a Plesk DNS master) is getting spammed with senseless DNS requests. The origin IPs of those ...
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1answer
241 views

IPTABLES block User-Agent

I get DDoS by the Wordpress Pingback BOTNET, now I want to block all client who contain Wordpress in there Useragents. For example: WordPress/4.0; http://vk.lokos.net; verifying pingback from ...
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0answers
174 views

Make NGINX Block All Requests To Direct Server IP - Stop XML-RPC Attacks

Essentially, my website is being attacked by a layer 7 XML-RPC attack and is currently offline and has been offline so I am in need of desperate help. Any assistance would be greatly appreciated :)! ...
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1answer
87 views

DOS and DDOS attacks [closed]

Our website is being constantly attacked by the bots. We tried mod_evasive and mode_security but those modules slowed our server considerably. Can anybody please suggest more solutions. Thanks in ...
2
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0answers
32 views

Getting DDoSed with requests for links to other sites and Bittorrent and BingBar [duplicate]

The other day my server started getting slow and the logs showed it was being heavily spammed with strange requests like for BingBar, 218.94.73.210 - - [22/Apr/2015:13:25:37 +1200] "GET ...
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0answers
63 views

Kernel panic under DDOS

I'm running a Debian 6 - 64bit system (Kernel 2.6.32-5-amd64) and often get flooded with DDOS. I have tuned the network parameters under /etc/sysctl.conf to not let any kernel parameter overflow. ...
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votes
2answers
77 views

IPTables not blocking IPStresser [closed]

I have been trying four days to block DDoS attacks with no success. I want to block anything that isn't whitelisted. This is my idea on OS Centos 7: //Delete All Existing Rules iptables --flush ...
1
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1answer
37 views

what would be the Impact of using Multiple sites in same VPC on AWS platform?

I have a site running on four server inside of a VPC on aws platform. My question is would their be any impact on site if I host another website on four new server in the same VPC considering their ...
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0answers
20 views

How do I ban IP's that request files that do not exist using fail2ban? [duplicate]

I have recently started using Fail2Ban and need to configure a specific 'Jail'. My apache error logs are filled with requests for files within my /var/www folder. The folder doesn't contain any ...
0
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1answer
96 views

How to block ApacheBench from sending requests to server?

I'm using Ubuntu 14.10, Apache 2.4. My server is under a huge DDoS attack right now, I tried to use mod_security , fail2ban and blocking attacking IPs manually using iptables and nothing worked. The ...
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1answer
83 views

How to defense a DDoS powered by end user's browser?

Like what Github.com has just experienced, what if a script provider, such as google ads, google analysis or something similar, add a malicious scripts at the end of their script, and let end users ...
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3answers
114 views

What is the most effective way to block IP address in Application Layer?

I understand that most Routers/Firewalls are able to block IP tables in the network level. IPtables for instance is quite effective. However, I want an application layer IP block.I have an HAproxy ...
0
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0answers
43 views

“eth0: link up” kernel panick on debian - DDoS attack or soft / device issue

A few hours ago my dedicated machine in Hetzner went down. I was thinking what that was DDoS attack, or Hetzner network problem. But my other machine was working fine. So i loggined into Hetzner and ...
0
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1answer
180 views

Iptables block layer 7 DDoS attacks

Recently I've been experiencing lots of layer 7 ddos attacks to my website. Specifically an HTTP GET request flood on the index page. (~20k r/s), my server is at OVH, so it's not overloading the pipe, ...
1
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1answer
93 views

Benefits of separate firewall product over AWS Security Groups for spam requests

I have a question that is an extension of this one: Examples where an AWS Security Group is not sufficient as a firewall?. Initially, the answer in that question made sense to me and I was working ...
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0answers
33 views

How can node addition/substraction be done while keeping randomness 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 ...
0
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1answer
31 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 ...
0
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1answer
37 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 ...
0
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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 ...
0
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1answer
46 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
votes
1answer
55 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 ...
0
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2answers
283 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 ...
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1answer
93 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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1answer
52 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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1answer
83 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 ...
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0answers
28 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 ...
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0answers
202 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, ...
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1answer
165 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 ...
5
votes
2answers
194 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 ...