Denial of service attack, is an attempt through some means to make a computer or network resource unavailable.

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Is it normal to collapse VPS CPU with this script?

This is the script, it comes with mod_evasive: #!/usr/bin/perl #test.pl: small script to test mod_dosevasive's effectiveness use IO::Socket; use strict; for(0..100) { my($response); ...
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defend dos attack

my website is crippled due to simple request from many ranges of ips, tens of thousands or more request per second. Is there a way to defend this kind of attack? Is there a way to trace back to the ...
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247 views

iptables logs but doesn't drop packets

I am trying to create some simple iptables DOS protection rules for my web server. I was doing testing on the following rules: iptables -N LOGDROP > /dev/null 2> /dev/null iptables -F LOGDROP ...
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Can't figure out this attack, getting botnets and something else

About two months ago a site of mine started getting some sort of attack, and after further investigation I found it to be botnet zombies and something else which I can't figure out. My site is not ...
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2answers
907 views

Is my server being used as a proxy or is a DOS underway? Lots of traffic in my apache log

I have a slice with a hosting provider that has a basic lamp stack setup. I was checking my apache logs today and I'm getting total random (it seems) request to my apache server. For instance, here ...
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2answers
134 views

In what way am I more likely to be DDoS'd? Via http or other ports? [duplicate]

I am writing a web service that has a lot of vicious competitors. Vicious as in: people have been getting DDoS'd within hours of setting up shop in this arena. The service will consist of: a ...
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8k views

DOS attack “slow post” : How to prevent in IIS

I have a public facing IIS 7.5 web server running a single ASP.NET website, which has just failed one of our security scans with a "slow post" vulnerability. Have tried reducing the httpruntime ...
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191 views

Apache relaying to prevent DoS

I've been wondering, is there a technology that relays (slows down) responses to a given IP according to the rate It makes requests? E.g I have an apache server with a "heavy" API service that I want ...
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75 views

What is idea of web server attack on thinker/js/think.js?

My web server is getting a lot of GET request on thinker/js/think.js and thinker/showSimilarInfo.do. These requests obviously constitute a server attacks. What is point of these attacks? Also, ...
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3k views

Why are NginX and Lighttpd not affected by Slowloris?

I am investigating the vulnerability to Slowloris and I think I understand how and why this sort of attack works. What I don't understand is why Lighttpd and NginX are not affected (according to the ...
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1k views

Ec2 Denial of Service: Securing cloud based website from DOS attack

How can I prep up my website infrastructure running on an EC2 instance against DOS attacks? I run apache with nginx as reverse proxy
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786 views

Windows Server 2008 Denial of Service Detection

We have a Windows 2008 server that hosts a file share in which a SQL server database is stored and accessed from another SQL server on the same network. Periodically, the database become inaccessible ...
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Protecting against UDP flood

One of my servers is being flooded with udp packets on random ports. 12:11:54.190442 IP 182.48.38.227.60173 > localhost.51523: UDP, length 1 12:11:54.190447 IP 182.48.38.227.60173 > ...
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2answers
1k views

DDoS Attacks on Game Servers [duplicate]

We run a fairly large game server hosting company with about 60 machines running Server 2008, and DDoS attacks something we have been dealing with for a long time. Unfortunately, due to the prices of ...
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3answers
402 views

Somebody eating all our bandwidth, what should I do?

OK, this is frustrating, my site got thousands of page views/connections in the last 3 days and finally we ran out of monthly bandwidth. We bought more bandwidth and closed the site for maintenance. ...
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454 views

Detecting DOS attack

On one of our systems we see many requests that take 75 seconds. Under low traffic responses are ca 0.3 seconds. What I am wondering is if someone is trying to keep connections open in order to ...
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505 views

Fail2ban advice on banning IP's and HTTP

I've recently installed fail2ban as a way of keeping one of our web servers secure from SSH attacks and HTTP attacks. At the moment I'm getting a lot of ssh attacks but fail2ban are banning and then ...
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2answers
923 views

Protecting against Keep-Dead Denial of service

i thought my server was safe with http-guardian but apparently not. Some smart arse keeps hitting my server with 'Keep-Dead' and causing it to crash. I've looked through the logs but can't see ...
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2k views

Logging Timeout'd Request in Apache 2.X

I am migrating some applications from Apache 1.3 to 2.2. We used to run some tests where attacker opens some HTTP connection to our server, and do nothing. Apache 1.3 would log the following 408 ...
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231 views

CentOS Server keeps grinding to a halt, then comes back up

CentOS 5.2 LAMP server The server slows down to a point where no services are responding. After a few minutes, it comes back and is running well. The server keeps doing this cycle, what could be ...
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277 views

DDOS Mitigation Services [duplicate]

Over the past week we have been a victim of two seperate ddos attacks varying in scale. The last one was very large and very hard to mitigate. We are looking at solutions from veriSign and Akamai ...
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713 views

what should be limit to use for IPTABLE rate limiting for a webserver

I see on my webserver some logs as follows 203.252.157.98 - :25:02 "GET //phpmyadmin/ HTTP/1.1" 404 393 "-" "Made by ZmEu @ WhiteHat Team - www.whitehat.ro" 203.252.157.98 - :25:03 "GET ...
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1answer
1k views

How do I prevent against a DOS attack through Outlook Web Access?

If I configure an Active Directory Lockout Policy, then someone can use repeated bad login attempts to lock users out. How do I block an IP if enough bad login attempts come from it? Can I do this ...
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3answers
591 views

DDOS by several IPs with one connection [duplicate]

I have a site that was being hit with a DDOS the same time every day for the past month, and after spending a month researching and pinpointing the bug, we enacted a bash script which if the ...
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3answers
453 views

Measure bandwidth by client IP in realtime

I have been recently attacked using DoS attack on random ports. I wasn't able to get the attackers IP and now I would like to find it. What tool can show me bandwidth (in Kbits/Mbits) used by each ...
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436 views

Detecting server abuse

Is there any standard way to prevent shared web servers from being abused? I run a CPanel box with a few people on it, and I get the occasional person that decides to use it to DoS other websites. ...
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3answers
932 views

Apache mod status is showing ..reading

Recently my apache got DoS attack, it happened attacker flood SYN request to our apache, i know because at that time i have wireshark enabled. After the attack finished, i restart my apache and its ...
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2answers
460 views

How do you stop PINGs from causing a DOS on a Linux server?

Have a CentOS-5.x box that appears to be going down as a result of PINGs. If the server gets PINGs it stops replying to ssh/http connections. Appears iptable is one approach, but I want to make sure ...
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4answers
719 views

Preventing Denial of Service Attacks

What's the most effecient way to prevent DoS attacks for game servers? Currently I do something like this: iptables -A INPUT -p udp --dport 27015 -m length --length 28 -j DROP Is it the best way?
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Strange DNS DOS attack — Endless Recursive Queries for <blank domain>

Our W2K3 DNS servers seem to be under some kind of DOS attack, but I can't seem to find any description of, or rationale for the attack. Three specific remote hosts have been bombarding two of our ...
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619 views

Ping size limit - FreeBSD

In the man page for FreeBSD ping: -s packetsize Specify the number of data bytes to be sent. The default is 56, which translates into 64 ICMP data bytes when combined with the 8 ...
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121 views

How can I recognize flooding? [closed]

how can I discover if my server is performing some illegal actions, like flooding?
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287 views

Is it possible to distinguish from “good” http requests and DoS attacks?

How could I know that a lot of requests in a short period of time come from a DoS attack and not from normal browser requests?
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186 views

How are suspected DoS attacks handled by webservers?

I rent a server somewhere out in Canada or so that I'm using to host a website of mine. That website has close to 400,000 pages that I wanted to index today. For that, I wrote a crawler a while back ...
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Has anyone experienced unintentional traffic overload due to clients' use of wget?

I am wondering if it is wise to indiscriminately block wget on servers that I maintain. Has anyone experienced unintentional traffic overload due to clients' use of wget?
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635 views

Is SYN flooding still a threat?

Well recently I've been reading about different Denial of Service methods. One method that kind of stuck out was SYN flooding. I'm a member of some not-so-nice forums, and someone was selling a python ...
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1answer
973 views

SYN flooding still a threat to servers?

Well recently I've been reading about different Denial of Service methods. One method that kind of stuck out was SYN flooding. I'm a member of some not-so-nice forums, and someone was selling a python ...
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3answers
453 views

Is it good to defense for DOS attacks with 2 request/sec?

Lots of example told me to defense with 5 or 4 request per second. Because usually a visitor clicking about in 1 or 2 links in one second, I think defense with 2 request per second is just fine. But ...
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Servers harrassed by individual on constantly changing IPs

We run a community product. There is an individual (a little PoS kid) in the UK that is harassing our site for the last 6 months. His daily task is to create a new account, post a bunch of illegal / ...
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Brainstorm: Flood/DoS/DDoS Attack prevention ideas

This is not a question asking how to stop an attack. This is simply a thread for anyone and everyone to discuss ideas for preventing, dealing with, and keeping your server alive during these attacks. ...
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Stopping a DOS attack

One of the sites I work with has recently started to get DoS'd. It started out at 30k RPS and now it's at 50k/min. The IP's are pretty much all unique, not in the same subnet, and are in multiple ...
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Best way to use large IP blacklist to deny access to a Windows 2008 web server?

Basically, I'm looking for a solution similar to the ones mentioned in a similar (but Linux-focussed thread) located here so that I can deny access to blacklisted IPs. I am specifically focussed on ...
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How do I block specific IPs and IP ranges in IIS7?

I'm trying to block various IP addresses from every site that I have hosted from an server running Windows 2008 and IIS7. I've found various information about how to do this using Deny rules from ...
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405 views

Finding Evidence of a Denial of Service Attack (Linux)

We had a Gentoo Linux server (that was updated weekly or bi weekly) that higher ups claimed did a denial of service attack on the whole local network and brought it down. Are there any log files we ...
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299 views

Repetitive / incessant hits to pages, blank referrer, non-malicious

I asked this question last week, and followed the debugging advice and now have additional information. I have an odd problem-- on a high traffic website (millions of visitors a month), every day we ...
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3answers
479 views

How to stop repetitive hits from same host to same URL?

I have an odd problem-- on a high traffic website (millions of visitors a month), every day we get about 20 or so situations where one host begins incessantly requesting the same page, over and over-- ...
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169 views

What is the best way to prevent somone abusing access to your site using scripts?

What is the best way to prevent someone abusing access to your site using scripts?
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6answers
573 views

Securing against DDoS [duplicate]

My client would like to have his eCommerce (custom-made) site secured from DDoS attacks. What strategies can I implement? There are multiple forms in the purchasing flow --- searching, drilling-down ...
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HTTP server, SYN flooding, and DoS attack questions

I am making an http server in c. It is in a pre-alpha stage but seemed to be stable enough to deploy on my server and run 4 minimal websites. It has been running seamlessly for two days until this ...
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MSSQL 2005 on port 1433 gets DOS from infected servers

I have a SQL Server 2005 server hosted outside my firewall at a data center. It is fully up-to-date on patches, etc. There's some old MSSQL worm (Slammer?) that STILL infects thousands of servers ...