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From: InfoSec News (alertsinfosecnews.org)
Date: Mon Nov 05 2007 - 00:15:18 CST
By Roger A. Grimes
November 02, 2007
In April of this year, Estonia suffered under a huge denial-of-service
attack. Lest you think that Estonia is some little, underprepared
country that doesn't follow basic computer security practices, you need
to know that the same thing could happen to your country.
Today's Internet is so screwed up, security-wise, that there is
absolutely nothing any country has that would stop a massive distributed
DDoS (denial of service) attack. Think SQL Slammer worm, but using
millions of bots designed to cause traffic floods. Bot nets under the
control of one malicious hacker (or group) are often measured into the
hundreds of thousands of nodes and, some analysts say, millions of
compromised machines. If a very large bot net was used to attack a
single country's Internet backbone, it would take that country -- even
the most technology-savvy nation -- a few days to get legitimate traffic
going again at previous levels.
Worrying about country-sized attacks isn't in most of our job
descriptions, but mitigating smaller DDoS attacks against our
organization are. To find out what most administrators could do to
mitigate DDoS attacks against their company, I spoke to an administrator
who has been there and done that: Paul Laudanski, founder and leader of
The effects of DDoS
Paul and his wife, Robin, lead the CastleCops site, which is the
headquarters of a volunteer organization dedicated to fighting malware,
spam, and phishing. They are very successful in getting malicious Web
sites and compromised computers shut down. They also provide advice in
Internet crime investigation and help others preserve evidence useful to
law enforcement. CastleCops has been in business since 2002 and, by
independent conservative calculations, prevented more than $150 million
in losses. This fact is not lost on the criminals who rule the Internet
today. CastleCops has been the target of more than a dozen DDoS attacks.
This year, it was subjected to two large gigabit-per-second DDoS attacks
that caused connection problems for many days. CastleCops followed its
own advice and Greg King has been charged in one of the attacks. You
should read more details of the attack to understand how something
similar could affect you.
I asked Paul what the average entity could do to mitigate the damage
from a large DDoS attack. He said, "The first thing you need to do is
decide whether you want to stay in business during the attack or not. If
you want to stay in business, you'll need to absorb all the attack
traffic along with your legitimate traffic. This means your broadband
connection, routers, firewall, Web servers, and back-end databases have
to be able to deal with the attack. Talk to your ISP: at many ISPs,
traffic levels above 2Gbps will get you billed at the 95th percentile.
If our ISP had committed us to that rate, CastleCops would have incurred
a $33,000 bill for a few days of DDoS traffic, which would have put our
mostly volunteer organization out of business. Find out ahead of time
how your ISP will handle DDoS events, and how you will be billed."
Paul continued, "I think many sites will need to scale to handle
10Gbps-to-30Gbps traffic loads." DDoS attackers will often start at
lower traffic levels and attempt to increase the pain until your ISP, an
upstream neighbor, or your servers fold. Although DDoS attacks above
10Gbps to 30Gbps occur, they are rare.
I asked Paul what administrators could do next to mitigate the attack.
He offered, "Turn on your server and equipment logging to give you as
much detail as possible. For example, Apache Web servers log connections
by default, but not in enough detail. You'll want to get direct and
forwarded IP addresses (to catch proxied connections), content details,
user agents, and referral addresses." Then, using the information you
collect, you can normally find a pattern to the DDoS traffic and place a
filter on intervening devices to drop the malicious packets. Determined
DDoS hackers will often change the pattern, so you will need to be on
your feet and realize that implementing your first filter doesn't mean
the DDoS is over.
Riding the DDoS storm
You can use an anti-DDoS mitigation service, such as Prolexic, to help
out. Essentially, you change your Web server's public IP address (the
DNS A record) to point to the mitigation service's IP address. They will
scrub out the bad traffic and pass back the good traffic. You can also
buy routers and network defense devices (such as Cisco or Juniper) built
to take down DDoS attacks. Some of the devices will start working right
away, putting down malicious traffic from the start, while others have
to be plugged in a few weeks ahead of time to learn the difference
between legitimate and anomalous traffic.
If you are ready to pursue possible criminal charges against the
attacker, collect the best evidence you can and call your local or
national authorities tasked with following up on Internet crime. In the
United States, contact your local FBI field office. They will direct you
to the appropriate division. It makes sense to have the appropriate
numbers researched and documented ahead of time. From the time that you
make the call, follow the recommendations of law enforcement.
One of the reasons that it helps to bring in law enforcement is getting
the legal authority to track the attack back to the originator. Law
enforcement can help with finding the bot net's command-and-control
(C&C) servers, which might lead to the hacker. Using the detailed
traffic you have collected, you should be able to identify some of the
originating IP addresses of the bot attack traffic. You (or law
enforcement) can contact the owner of the IP addresses and request a
forensic copy of the malware, which can be dissected to find the C&C
server's IP address, which in turn can be used to find the hacker's
To be honest, being able to locate and prosecute the DDoS attacker is a
long shot. The lack of cohesive communications between all the parties
that need to be involved in an investigation, the legal implications of
the global nature of the assault, and the growing sophistication of bot
nets all fight against a successful prosecution. But as Paul and
CastleCops can tell you, it can be done.
Roger A. Grimes is contributing editor of the InfoWorld Test Center. He
also writes the Security Adviser blog and the Security Adviser column.
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