Apache Throttling Itself?

[Lisa Kachold]

Might need a nice mod_security rule for this one hit?

Or you have a distributed DoS attack (on conjunction with phishing and
pharming [do you take credit cards or get a boatload of hits?])

See:  http://isc.sans.org/diary.html?storyid=6601&rss

In considering the ramifcations of a slow denial of service attack
against particular services, rather than flooding networks, a concept
emerged that would allow a single machine to take down another
machine's web server with minimal bandwidth and side effects on
unrelated services and ports. The ideal situation for many denial of
service attacks is where all other services remain intact but the
webserver itself is completely inaccessible. Slowloris was born from
this concept, and is therefore relatively very stealthy compared to
most flooding tools.

Slowloris holds connections open by sending partial HTTP requests. It
continues to send subsequent headers at regular intervals to keep the
sockets from closing. In this way webservers can be quickly tied up.
In particular, servers that have threading will tend to be vulnerable,
by virtue of the fact that they attempt to limit the amount of
threading they'll allow. Slowloris must wait for all the sockets to
become available before it's successful at consuming them, so if it's
a high traffic website, it may take a while for the site to free up
it's sockets. So while you may be unable to see the website from your
vantage point, others may still be able to see it until all sockets
are freed by them and consumed by Slowloris. This is because other
users of the system must finish their requests before the sockets
become available for Slowloris to consume. If others re-initiate their
connections in that brief time-period they'll still be able to see the
site. So it's a bit of a race condition, but one that Slowloris will
eventually always win - and sooner than later.

On 6/18/09, Stephen <cryptworks at gmail.com> wrote:
> I have some Dermal Adhesive at home if you need me to bring it :-)
>
> On Wed, Jun 17, 2009 at 6:48 PM, <fouldragon at aol.com> wrote:
>> Today's new lesson:  mod_evasive
>>
>> Set up on the new server, not the old one.  Now can someone help me
>> glue my hair back on?
>>
>>
>> -----Original Message-----
>> From: Alex Dean <alex at crackpot.org>
>> To: Main PLUG discussion list <plug-discuss at lists.plug.phoenix.az.us>
>> Sent: Tue, Jun 16, 2009 7:06 pm
>> Subject: Re: Apache Throttling Itself?
>>
>>
>>
>>
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>> On Jun 16, 2009, at 8:35 PM, Alex Dean wrote:
>>
>>
>>> You have some badly-optimized query which is slowing the whole >
>> process down.
>>
>>
>> This should read "You *could* have some badly-optimized query...".
>> Sorry.
>>
>>
>> alex
>>
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>>
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>
>
>
> --
> A mouse trap, placed on top of your alarm clock, will prevent you from
> rolling over and going back to sleep after you hit the snooze button.
>
> Stephen
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