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 to stop DDOS from unique ip addresses? [duplicate]

I have a problem with a LAMP server where Apache keeps getting lots of request "POST / HTTP/1.1" but always from new IP addresses. Blocking the IPs using iptables obviously won't help. Any ideas how ...
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1answer
47 views

Under attack what source url source would this be? [duplicate]

We are under attack since about 2 weeks now and did as much as we can to protect oursefs. mod_reqtimeout is doing the job now but I am confused as what is it that they are hiting I found this post ...
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2answers
422 views

How to prevent DDoS attacks? [duplicate]

I am a creator of a flash game server. I use cloudflare for my site, however the game tcp server cant be protected by CloudFlare. For about 2 months some person DDoSes my game using direct ip. Every ...
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71 views

DDOS on Mail server? [duplicate]

My server has been down most of the day, running top shows several Apache processes (httpd) each one using 70% or more of the CPU, and MySql eating almost all memory. I have tried rebooting the ...
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1answer
203 views

How to prevent Skype DDOS [duplicate]

Is there a way to monitor number of attempted Skype connections on a specified port and dynamically firewall off the offending IPs if they break a certain threshhold within a specific time limit - in ...
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1k views

Blocking UDP packets with a length of 4

My server is being flooded with UDP packets with a length of 4 (header is 32 bytes). 04:56:26.844797 IP 108.241.236.114.47034 > 185.5.173.249.14522: UDP, length 4 04:56:26.844831 IP ...
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2answers
777 views

HTTP attack - Too many connections & TIME_WAIT

I am running CentOS 6 with http -2.2.15 Going under HTTP attack, i can see many http process running. > netstat -nat | awk '{print $6}' | sort | uniq -c | sort -n > 1 established) > ...
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2answers
782 views

Defensing againt DDoS attack on Squid server [duplicate]

My Squid (3.1.20 on Ubuntu 13.04) is under DDoS attack (with about 1000 different IPs). I'm using Basic Authentication on it and all of those requests are getting DENIED response but still they ...
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762 views

Is My Website Under DDOS Attack? [closed]

Recently I noticed that the CPU load of my server is increasing rapidly. In any day, the CPU load does not reach 2.5. I have the following server: Intel® Xeon® E3-1270 v2 Single Processor - Quad Core ...
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1answer
158 views

How to protect from DDOS attack that is coming from an exit node

Newroz Telecom (an ISP) is using an exit node (or gateway) for each city they operate in. That is all the users in city A is sharing one public IP (when the users go to a website to show their IP they ...
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191 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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252 views

What amount of effort and money should one invest against DDoS threats? [closed]

Typically, when you invest money to protect yourself against some possible threat, you should take into account two factors: the probability (p) of the problem actually happening how much money (m) ...
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97 views

What is the best way to compare vhost traffic? [closed]

Recently one of my servers has been subjected to malicious ddos attacks. I have about 12 websites hosted on the server which uses name based v-hosting. I am trying to identify which virtual host(s) ...
2
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1answer
208 views

Received Notification of my server be involved in “DNS amplification attack”. How can I stop? [duplicate]

I just received an email from my website internet provider that my server has been "involved as open resolvers in DDoS attacks (DNS Reflection) over the past few weeks." Here is the full email: ...
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2answers
2k views

httpd high cpu usage slowing down server response [duplicate]

my client has a image sharing website with about 100.000 visitor per day it has been slowed down considerably since this morning when i checked processes i've notice high cpu usage from http .... ...
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1answer
83 views

DDoS attacks are killing all my services [duplicate]

I've a few servers running as ssh proxy, someone started to DDOS me, i've installed ddos deflate and apf. The traffic made by ddos downgrade from 10 MB/s to 1 MB/s but it still make my users kick from ...
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4answers
79 views

How to identify which website on my instance is receiving lots of traffic?

I am new to server administration and have just setup a new quad core instance which hosts around 15 websites. Over the past couple of days my server load has been averaging at around 15.00. I ...
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1answer
590 views

problems simulating TCP SYN flood

I'm trying to simulate a TCP SYN flood to tune a web server (planning to deploy on AWS). I setup a 'target' VM, disabled iptables and running hping (hping -p 80 -i u1000 -c 1000 -S destaddr) from ...
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1answer
1k views

IPTables : prevent UDP Flooding

I want to stop the UDP flooding on the Linux device. I have written a simple IPTable rule to drop all UDP packets iptables -A INPUT -p udp DROP But still the DoS attack happens and the device gets ...
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6answers
8k views

Tools for simulating DDoS attacks

I wanted to test my website if it can sustain strong DDoS's, but I don't know which tools could I use to simulate them in my website. What tools are used to simulate DDoS? I found bonesi but it was ...
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1answer
586 views

Outlook for Mac, Active Directory DNS and DDOS

Edit: This is not a question about DDOS, but a question about how to resolve a technical issue impacting only Mac clients of Outlook Anywhere. Problem and solution are are now known, but I cannot ...
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1answer
132 views

can I filter TCP SYN packets with seq=0

My servers appear to be targeted by a SYN-flood attack. Between 50-600MBit/s, spoofed IPs. Packets look like this: IP p.q.r.s.1234 > my.ser.vers.ip.80: Flags [S], seq 0, win 5840, length 0 with ...
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702 views

Mitigate DDoS attack by Null-routing my server's IP?

My services were attacked by what appears to be a botnet of quite a large number of computers. Since all my servers have additional IPs, and my hosting provider lets me null-route my IP addresses to ...
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1k views

Prevent DNS responses for specific domain completely

Situation: Server (Win 2008R2) is being used in a DNS (amplification) DDoS attack. Amplification factor is already down to 1: Set the DNS server to non-recursive and removed all root hints -> DNS ...
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224 views

Can the netstat command show what specific website a user is on? [closed]

I'm currently under an Apache DDoS attack and have 13 websites shared under one server. I can use the netstat command to see the # of connections per IP, but not what website they're actually on. I ...
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423 views

Can you block an ip with multiple connections? (Apache ddos attack)

My server is under a Apache ddos attack right now. There's a ton of single ip addresses with 30+ connections. When I use this SSH command: netstat -n | grep ':80' | awk -F' ' '{print $5}' | awk ...
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2answers
293 views

Router DDoS Protection by MAC [duplicate]

I was wondering if there are any DDoS defences where a (any) router will block all packets (for any period of time) from the MAC address of its attacker. If so, under what circumstances would this ...
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0answers
78 views

How to prevent HTTP-based DDoS attacks [duplicate]

This night, I've noticed nginx was not responding to requests. After some investigation, I found that it was using 100% of the CPU and error.log was full of messages like this one: 2013/05/28 ...
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1answer
65 views

Send mails from secondary server

Problem: When I send an email from my server, the email headers contain the IP address of the server. Yeah, this is a problem, because the server is being the target of DDoS attacks. Using CloudFlare ...
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1answer
700 views

Ubuntu Server DDoS protection [duplicate]

I've seen many articles on DDoS protection, but none work. I need protection for a socket server i'm running on the server. It's running on port 9876 and it's for a flash-based game. when it gets ...
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408 views

How to protect Nginx from HULK DoS tool

There is a tool called HULK (Http Unbearable Load King). It's a web server denial of service tool. It is designed to generate volumes of unique and obfuscated traffic at a webserver, bypassing caching ...
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904 views

Nginx - Redirect request by GET parameters pattern

One of my servers was attacked by DDoS a couple of days ago and it lasted for 4 days. Below are the logs snippet of the request: 36.224.180.253 - - [14/May/2013:03:11:46 +0800] "GET ...
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1answer
136 views

Traffic backlogged after (D)DoS attack? [closed]

About 25 hours ago, I got an e-mail from UptimeRobot (uptimerobot.com) telling me that me websites had gone down. I raced over to my server room, where my TP-Link router was completely unresponsive ...
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1answer
5k views

How to configure mod_reqtimeout in Apache2

I need to configure mod_reqtimeout in my Apache server v2.2.22 (in a linux machine). Problem is, I have absolutely no clue on how to do it. I checked the Apache site on this module at this link but ...
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1answer
290 views

How to block an IP, if it is making many http/apache/mysql requests in a second?

If some one tried force burst attack on my website, how can i block their IP address? I mean, I want to block an IP if I am getting many http/Apache/SQL requests per second from it. How can i prevent ...
4
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1answer
231 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
819 views

Anti-DDos Apache2 Fail2ban regex rule [duplicate]

I have fail2ban up and running, but my Failregex doesnt match anything, something is wrong. Request which i like to ban look like this: 186.6.65.199 - - [06/May/2013:18:46:21 +0400] "GET / HTTP/1.1" ...
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269 views

Parse Apache logfile and ban IPs

My server is under attack, it is flooded with request with the following pattern: Thousands of IPs Each IP request the same page "GET / HTTP/1.1" with the same referrer 3-5 times per second (same ...
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1answer
546 views

Any way to Improve performance of iptables DDOS whitelist? [closed]

I'm having a problem stopping a DDOS attack on a dedicated server. I have tried a lot of things (mod_evasive, apf, ddos deflate, bfd...). The attack is very big and from a lot of differents IPs, and ...
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2answers
646 views

How to properly drop ICMP type 3 packets on possible DDoS attack?

Even after running iptables -A INPUT -p icmp -m icmp --icmp-type 3 -j DROP I keep getting ICMP type 3 code 13 packets on tcpdump. when I run tcpdump icmp, I get messages like: 19:41:31.923630 IP ...
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1answer
1k views

ICMP time exceeded in-transit

In the last few days my server suffers an attack of this kind: (bandwith > 60MBit/s, XXX.XXX.XXX.XXX are multiple IPs) tcpdump -n proto ICMP 17:15:19.267464 IP XXX.XXX.XXX.XXX > my_ip: ...
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1answer
291 views

Find IP addresses with most connections on system

I am currently experiencing some attacks on my OpenVZ server (CentOS 6.3 64bit), which is saturating the public ethernet interface (currently accessing SSH via the private interface). Is it possible ...
0
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2answers
82 views

Will I get banned or blocked for running a diagnostic app?

This may seem like a simple question. Hopefully it will have a simple answer. I run an internet radio station. There are 3 machines. Music source client Stage server Master server (relays the ...
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155 views

Lot of Apache requests in “L” state, what could be the reason? DDOS?

I am having this in my apache server status message: LLLLLLLLLLLLLLLWLLLLLLLLWLLLLLWLLLLLLLLLLWLLLLLLLWLLLLLLLLLLLLLL WLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLWLWLLLLLLLLL ...
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3answers
845 views

iptables rule to stop DDOS [duplicate]

My server is undergoing a ddos attack with the traffic in my apache logs appearing like: ip address - - [11/Apr/2013:01:01:04 -0600] "POST / HTTP/1.1" 416 31 "-" "Microsoft Internet Explorer" ip ...
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3answers
457 views

I think I'm under DoS attack. How can I respond?

My server's CPU has been spiking out for the past few days, to the point that it drops requests. I've been looking through the logs, and see certain IP's in the logs that are just simply downloading ...
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251 views

Block incoming DNS queries using netsh advfirewall

How do you do this with Windows firewall? iptables -I INPUT --in-interface ! lo -p udp --dport 53 -j DROP Ideally, if you can do this with netsh and so that it will survive whatever it is that ...
3
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1answer
462 views

iptables, what to open on INPUT for wget

I am configuring my iptables. The policy for OUTPUT is ACCEPT. Though INPUT is DROP. I am wondering what I need to open up on INPUT so I can receive responses on outgoing traffic (automatic or manual, ...
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1answer
132 views

ssyn.c and slow.c used on my VPS [duplicate]

I have noticed some changes on VPS Debian Squeeze and looked with history to see what commands were run. Then I found some which I'm 100% sure I didn't run because I don't know what are they. Somebody ...
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147 views

Tool to automatic suspending the DDOSed website before the whole VPS is being suspended by Data center [duplicate]

I have a non-Xen VPS (don't exactly know what the software is). The past week, we had experienced several DDOS attacks on one (or some) of the hosts and because of using more than usual bandwidth, ...