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

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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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4answers
2k views

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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4answers
1k views

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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2answers
1k views

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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3answers
29k views

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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2answers
412 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 ...
1
vote
1answer
306 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 ...
2
votes
3answers
564 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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3answers
173 views

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

What is the best way to prevent someone abusing access to your site using scripts?
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6answers
574 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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2answers
5k views

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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5answers
2k views

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 ...
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4answers
193 views

rhel-5.3->vm wordpress attack

i have a rhel 5.3 w/ few virtual machines and one of virtual pc runs cpu: intel quad 2.83 mem: 3.5G os: Linux 2.6.18-128.1.14.el5xen #1 SMP Mon Jun 1 16:09:30 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux ...
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2answers
3k views

(D)DOS - tcpdump established connections analysis (too many established connections)

¿How can I debug this problem? (I've got full tcpdump captures) I have a TCP server into which many clients establish persistent connections. Normally all these clients behave, and I never reach ...
2
votes
3answers
6k views

Identifying DDOS Attacks on Windows 2008 Servers [duplicate]

I recently was notified by my monitoring service that a few Windows 2008 servers (hyper-v instances) were down. I logged into the Hyper-V box and noticed everything was super slow. I opened task ...
30
votes
7answers
19k views

How to best defend against a “slowloris” DOS attack against an Apache web server?

Recently a script called "slowloris" has gained attention. The basic concept of what slowloris does is not a new attack but given the recent attention I have seen a small increase in attacks against ...
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4answers
219 views

AD Domain Controllers being Slammed

My Windows Server 2008 Domain Controllers are getting hundreds of log in attempts per minute. For the most part the IP addresses are not in the Event Log however the ones that do occasionally show up ...
2
votes
5answers
660 views

DDoS attacks [duplicate]

How to prevent DDoS attacks on Windows/IIS servers ?
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3answers
527 views

Do reports of packet flooding suggest a DOS attacK?

Our E1 connection is being closed by our firewall*. It happens intermittently every few days. I find log entries like this one around the same time as the dropout: Jun 2 09:53:35 sg580 kernel: ...
3
votes
3answers
168 views

What criteria do you use to determine if someone is hammering your server?

When you go through your logs, what criteria do you use to determine if it's you (ie: you need to beef up your server/s) or them (ie: they're verging on a DoS)? How many connections/second would you ...
6
votes
4answers
988 views

Is account lockout a denial of service attack waiting to happen?

The default behaviour of windows is to lockout an account after a number of failed authentication attempts (usually three).. This means that with the following net use \\targetmachine\c$ ...
9
votes
5answers
1k views

What are the best techniques for preventing denial of service attacks?

Currently I have been using (D)DoS-Deflate to manage such situations on numerous remote servers, along with Apache JMeter for load testing. Overall it has been working fairly well, although I'd like ...
2
votes
2answers
618 views

What does the arxiv.org anti-bot “search and destroy” actually do?

The lanl.arxiv.org math and scientific preprint service (formerly known as xxx.lanl.gov) has a strict policy against bots that ignore its robots.txt, Robots Beware. On that page, the have a link ...
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3answers
1k views

Blocking IP addresses Load Balanced Cluster

We're using HAproxy as a front end load balancer / proxy and are looking for solutions to block random IP addresses from jamming the cluster. Is anyone familiar with a conf for HAProxy that can block ...