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

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iptables rate-limit module problem

I am using iptables' rate-limit module to prevent DoS attack (I know it cannot stop a full scale DDoS but at least it can help with smaller attacks). In my rules I have something like: ...
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1answer
566 views

Where can I find DoS attack simulator [closed]

I am taking a Security module and my project team intend to study DoS attacks by simulating them to better understand the mechanism, the damage and preventing mechanism, etc... Could someone please ...
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2answers
274 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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5answers
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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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1answer
860 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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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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1answer
465 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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3answers
533 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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1answer
3k 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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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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2answers
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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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4answers
754 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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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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1answer
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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2answers
295 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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2answers
144 views

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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1answer
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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
675 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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8answers
428 views

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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2answers
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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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2answers
413 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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1answer
310 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 ...
3
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3answers
609 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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5answers
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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 ...
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2answers
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(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 ...
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5answers
671 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: ...
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4answers
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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$ ...
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5answers
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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 ...