Mailinglist Archive: opensuse-security (232 mails)

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Re: [suse-security] Under DDoS Attack...
  • From: media Formel4 <info@xxxxxxxxxx>
  • Date: Thu, 27 Oct 2005 16:10:20 +0200
  • Message-id: <4360DFCC.1060802@xxxxxxxxxx>
Randall R Schulz schrieb:
Ralf,

You should not use your mail client's "reply" function to start a new topic thread.

Wooops - sorry, my bad :-(



On Thursday 27 October 2005 06:20, media Formel4 wrote:

Hi list,

right now we're experiencing a (for me) very uncommon DDoS attack
against one of our webservers. Looking with netstat we find hundreds
of established connections to our Apache webserver, but nothing in
the logs - which means the attacker opens up a connection (not only a
SYN request as in SYN flood attacks) and then blocks the Apache child
until it hits timeout. This attack comes from thousands of IP numbers
(bots?) all over the world.

Question is:

- Is it possible with spoofed IP numbers to establish connections to
port 80? As far as I know you should get stuck after "SYN".


Spoofing IPs probably isn't required. You could try running traceroutes on several of the remote IPs. You'll probably find they're in different places.

Nowadays there are black-hats out there who command compromised armies of always- or often-on hosts on high-speed Internet connections. When it suits their whim or their plan, they can enlist them to perform such a DDoS attack (or distributed attack).

That's what I thought too - but trying to trace back the IPs in question I find very often unrouted areas and non-reachable (but maybe firewalled) IPs

The reason I mentioned that question is that I found a group of 300 IPs coming from an american company network. I contacted them and they stated too, that those IPs were not in use and not routed right now...


- How can I secure this server and/or stop this attack?


Lower the Apache timeout?

Which will lead into a lot of problems for all running scripts needing more than x seconds to fetch data from databases and creating the output.

After restarting the webserver it takes from 15 seconds to 90 seconds to reach MaxClients...


Ralf Koch

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