By Mark Landler and John Markoff
The New York Times
May 29, 2007
TALLINN, Estonia, May 24 When Estonian authorities began removing a
bronze statue of a World War II-era Soviet soldier from a park in this
bustling Baltic seaport last month, they expected violent street
protests by Estonians of Russian descent.
They also knew from experience that if there are fights on the street,
there are going to be fights on the Internet, said Hillar Aarelaid, the
director of Estonias Computer Emergency Response Team. After all, for
people here the Internet is almost as vital as running water; it is used
routinely to vote, file their taxes, and, with their cellphones, to shop
or pay for parking.
What followed was what some here describe as the first war in
cyberspace, a monthlong campaign that has forced Estonian authorities to
defend their pint-size Baltic nation from a data flood that they say was
set off by orders from Russia or ethnic Russian sources in retaliation
for the removal of the statue.
The Estonians assert that an Internet address involved in the attacks
belonged to an official who works in the administration of Russias
president, Vladimir V. Putin.
The Russian government has denied any involvement in the attacks, which
came close to shutting down the countrys digital infrastructure,
clogging the Web sites of the president, the prime minister, Parliament
and other government agencies, staggering Estonias biggest bank and
overwhelming the sites of several daily newspapers.
It turned out to be a national security situation, Estonias defense
minister, Jaak Aaviksoo, said in an interview. It can effectively be
compared to when your ports are shut to the sea.
Computer security experts from NATO, the European Union, the United
States and Israel have since converged on Tallinn to offer help and to
learn what they can about cyberwar in the digital age.
This may well turn out to be a watershed in terms of widespread
awareness of the vulnerability of modern society, said Linton Wells II,
the principal deputy assistant secretary of defense for networks and
information integration at the Pentagon. It has gotten the attention of
a lot of people.
The authorities anticipated there would be a backlash to the removal of
the statue, which had become a rallying point for Estonias large
Russian-speaking minority, particularly as it was removed to a less
accessible military graveyard.
When the first digital intruders slipped into Estonian cyberspace at 10
p.m. on April 26, Mr. Aarelaid figured he was ready. He had erected
firewalls around government Web sites, set up extra computer servers and
put his staff on call for a busy week.
By April 29, Tallinns streets were calm again after two nights of riots
caused by the statues removal, but Estonias electronic Maginot Line was
crumbling. In one of the first strikes, a flood of junk messages was
thrown at the e-mail server of the Parliament, shutting it down. In
another, hackers broke into the Web site of the Reform Party, posting a
fake letter of apology from the prime minister, Andrus Ansip, for
ordering the removal of the highly symbolic statue.
At that point, Mr. Aarelaid, a former police officer, gathered security
experts from Estonias Internet service providers, banks, government
agencies and the police. He also drew on contacts in Finland, Germany,
Slovenia and other countries to help him track down and block suspicious
Internet addresses and halt traffic from computers as far away as Peru
The bulk of the cyberassaults used a technique known as a distributed
denial-of-service attack. By bombarding the countrys Web sites with
data, attackers can clog not only the countrys servers, but also its
routers and switches, the specialized devices that direct traffic on the
To magnify the assault, the hackers infiltrated computers around the
world with software known as bots, and banded them together in networks
to perform these incursions. The computers become unwitting foot
soldiers, or zombies, in a cyberattack.
In one case, the attackers sent a single huge burst of data to measure
the capacity of the network. Then, hours later, data from multiple
sources flowed into the system, rapidly reaching the upper limit of the
routers and switches.
By the end of the first week, the Estonians, with the help of
authorities in other countries, had become reasonably adept at filtering
out malicious data. Still, Mr. Aarelaid knew the worst was yet to come.
May 9 was Victory Day, the Russian holiday that marks the Soviet Unions
defeat of Nazi Germany and honors fallen Red Army soldiers. The Internet
was rife with plans to mark the occasion by taking down Estonias
Mr. Aarelaid huddled with security chiefs at the banks, urging them to
keep their services running. He was also under orders to protect an
important government briefing site. Other sites, like that of the
Estonian president, were sacrificed as low priorities.
The attackers used a giant network of bots perhaps as many as one
million computers in places as far away as the United States and Vietnam
to amplify the impact of their assault. In a sign of their financial
resources, there is evidence that they rented time on other so-called
When you combine very, very large packets of information with thousands
of machines, youve got the recipe for very damaging denial-of-service
attacks, said Jose Nazario, an expert on bots at Arbor Networks, an
Internet security firm in Ann Arbor, Mich.
In the early hours of May 9, traffic spiked to thousands of times the
normal flow. May 10 was heavier still, forcing Estonias biggest bank to
shut down its online service for more than an hour. Even now, the bank,
Hansabank, is under assault and continues to block access to 300 suspect
Internet addresses. It has had losses of at least $1 million.
Finally, on the afternoon of May 10, the attackers time on the rented
servers expired, and the botnet attacks fell off abruptly.
All told, Arbor Networks measured dozens of attacks. The 10 largest
assaults blasted streams of 90 megabits of data a second at Estonias
networks, lasting up to 10 hours each. That is a data load equivalent to
downloading the entire Windows XP operating system every six seconds for
Hillar and his guys are good, said Bill Woodcock, an American Internet
security expert who was also on hand to observe the response. There
arent a lot of other countries that could combat that on his level of
Estonias defense was not flawless. To block hostile data, it had to
close off large parts of its network to people outside the country.
It is really a shame that an Estonian businessman traveling abroad does
not have access to his bank account, said Linnar Viik, a computer
science professor and leader in Estonias high-tech industry. For members
of the Estonian Parliament, it meant four days without e-mail.
Still, Mr. Viik said the episode would serve as a learning experience.
The use of botnets, for example, illustrates how a cyberattack on a
single country can ensnare many other countries.
In recent years, cyberattacks have been associated with Middle East and
Serbian-Croatian conflicts. But computer systems at the Pentagon, NASA,
universities and research labs have been compromised in the past.
Scientists and researchers convened by the National Academy of Sciences
this year heard testimony from military strategy experts indicating that
both China and Russia have offensive information-warfare programs. The
United States is also said to have begun a cyberwarfare effort.
Though Estonia cannot be sure of the attackers identities, their plans
were posted on the Internet even before the attack began. On
Russian-language forums and chat groups, the investigators found
detailed instructions on how to send disruptive messages, and which
Estonian Web sites to use as targets.
We were watching them being set up in real time, said Mr. Aarelaid, who
weeks later could find several examples using Google.
For NATO, the attack may lead to a discussion of whether it needs to
modify its commitment to collective defense, enshrined in Article V of
the North Atlantic Treaty. Mr. Aarelaid said NATOs Internet security
experts said little but took copious notes during their visit.
Because of the murkiness of the Internet where attackers can mask their
identities by using the Internet addresses of others, or remotely
program distant computers to send data without their owners even knowing
it several experts said that the attackers would probably never be
caught. American government officials said that the nature of the
attacks suggested they were initiated by hacktivists, technical experts
who act independently from governments.
At the present time, we are not able to prove direct state links, Mr.
Aaviksoo, Estonias defense minister, said. All we can say is that a
server in our presidents office got a query from an I.P. address in the
Russian administration, he added, using the abbreviation for Internet
protocol. Moscow had offered no help in tracking down people who the
Estonian government believes may be involved.
A spokesman for the Kremlin, Dmitri S. Peskov, denied Russian state
involvement in the attacks and added, The Estonia side has to be
extremely careful when making accusations.
The police here arrested and then released a 19-year-old Estonian man of
Russian descent whom they suspected of helping to organize the attacks.
Meanwhile, Estonias foreign ministry has circulated a document that
lists several Internet addresses inside the Russian government that it
said took part in the attacks.
I dont think it was Russia, but who can tell? said Gadi Evron, a
computer security expert from Israel who spent four days in Tallinn
writing a post-mortem on the response for the Estonians. The Internet is
perfect for plausible deniability.
Mr. Evron, an executive at an Internet security firm called Beyond
Security, is a veteran of this kind of warfare. He set up the Computer
Emergency Response Team, or CERT, in Israel. Web sites in Israel are
regularly subjected to attacks by Palestinians or others sympathetic to
Whenever there is political tension, there is a cyber aftermath, Mr.
Evron said, noting that sites in Denmark became targets after a
newspaper there published satirical cartoons depicting the prophet
The attacks on Estonias systems are not over, but they have dropped in
volume and intensity, and are aimed mainly at banks. The last major wave
of attacks was on May 18.
Now that the onslaught has ebbed, Mr. Aarelaid is mopping up. A few days
ago, he managed to get to the sauna with Jaan Priisalu, the head of
computer security at Hansabank, and other friends from Estonias Internet
Im a simple I.T. guy, he said, gazing at a flickering computer screen. I
know a lot about bits and packets of data; I dont know about the bigger
questions. But somebody orchestrated this thing.
Mark Landler reported from Tallinn and John Markoff from San Francisco.
Steven Lee Myers contributed reporting from Moscow.
Copyright 2007 The New York Times Company
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