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Dos attackes on apache

Posted on 2002-06-28
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Last Modified: 2010-03-04
how to prevent DoS attackes on my apache web server (1.3.26)
these attackes are on a particular site (100 get request per second). due to this server server httpd process exceed their limit .
I also used tcp interest on cisco router but these attacks also exceed the tcp intercept blocking limit.
any help will be highly appreciated..
thanks
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Question by:shahid1
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by:samri
ID: 7116265
Shahid,

You have about 10 pending questions.  Please revisit the Q, and feedback the members that is/are already spent their quality time to help you :)

Back to the question about Dos Attach on apache;

To my knowledge, Apache there is no mechanism in Apache to detect such activity.  However, if we look at the nature of DoS attack, we might be able to hack apache a bit to at lest minimise the chances of getting the daemon to suck up system resources.

Off-hand, all I can think off is getting a firewall in between;  Might not be a good choice since it would involves time and/or money.

Another option, which I would think is possible is to control number of connection from a specific client/IP address.

This can be done using mod_throttle

http://www.snert.com/Software/mod_throttle/

I personally haven't tried to implement mod_throttle yet, that is why I cannot guarantee that I would work as expected.

Some readings on DoS attack on Apache:
http://www.linuxplanet.com/linuxplanet/tutorials/1527/1/

I kinda like this one from SANs:  You might need to register (free) to view the page;  But it is good.

http://rr.sans.org/sysadmin/apache.php

--- some excerpts from the site.
Security Related Directives - Buffer Overflow and HTTP DoS

  Covered in this section are several of the server security related directives and their purpose. There are
  many directives available with Apache. They can be found on the Apache HTTP Server Project Web Site
  http://httpd.apache.org/docs/mod/directives.html.

  Using following directives will help reduce the risk of DoS and Buffer Overflow attacks.

  Denial of Service attack (DoS).

  LimitRequestbody: Numeric parameter controlling maximum HTTP request body size.

  LimitRequestFields: Numeric parameter that limits allowable number of request headers.

  KeepAlive: Setting this parameter to off will disable a constant connection.

  KeepAliveTimeout: Limits the time Apache will wait for additional requests.

  Buffer Overflow attack.

  LimitRequestFieldSize: Limits the size of each request header.

  LimitRequestLine: Limits the length of each request line.
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Author Comment

by:shahid1
ID: 7129508
I am talking about yaha.E worm who generate actual and ligitimate http request for a particular web-site from infected computer.
and the server hosted that site goes down within no time.
these http requests go on increasing as worm spreads through out the world.

regd...shahids
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Expert Comment

by:samri
ID: 7129518
shahid1,

Thanks for the information.  I might be able to dig some threads here and there.

However, most article that I came across did mention that it is quite hard to control such attack, since it is done at OS layer.  Most sites would implement firewall, that has a predefined attack pattern.  I would suspect that yaha.E worm would need to flood an Apache at a high volume and high frequecy of request, and only the deamon would eventuall went down.  Most (or Some) firewall would trigger, and deny the source address is such pattern is detected.

The proposed solution- mod_throlle should be able to control the # of request, or interval between request.  This would at least slow down the attact, and let the apache daemon from taking too much resources, and bring the whole machine down.

cheers.
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Author Comment

by:shahid1
ID: 7129556
I am talking about yaha.E worm who generate actual and ligitimate http request for a particular web-site from infected computer.
and the server hosted that site goes down within no time.
these http requests go on increasing as worm spreads through out the world.

regd...shahids
0
 
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samri earned 200 total points
ID: 7130903
shahid,

accidental repeat or intentional repeats?

cheers
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Author Comment

by:shahid1
ID: 7131105
samri,
sorry, it was accidental.

shahids
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by:periwinkle
ID: 9690993
No comment has been added lately, so it's time to clean up this TA.

I will leave a recommendation in the Cleanup topic area with the following recommendation for this question:

Answered by samri

Please leave any comments here within the next seven days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

periwinkle
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Author Comment

by:shahid1
ID: 9737865
np
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