Critical systems whose network addresses would not be generally known were targeted, including those serving telephony and financial transaction processing. Although not all of the
computer crackers behind the cyberwarfare have been unveiled, some experts believed that such efforts exceed the skills of individual activists or even
organised crime as they require a
co-operation of a state and a large
telecom company. At the same time he called claims of Estonians regarding direct involvement of Russian government in the attacks "empty words, not supported by technical data". Professor
James Hendler, former chief scientist at
The Pentagon's
Defense Advanced Research Projects Agency (DARPA) characterised the attacks as "more like a cyber riot than a military attack." Arbor Networks operated
ATLAS threat analysis network, which, the company claimed, could "see" 80% of Internet traffic. Nazario suspected that different groups operating separate distributed botnets were involved in the attack. Experts interviewed by IT security resource SearchSecurity.com "say it's very unlikely this was a case of one government launching a coordinated cyberattack against another":
Johannes Ullrich, chief research officer of the Bethesda said "Attributing a distributed denial-of-service attack like this to a government is hard." "It may as well be a group of bot herders showing 'patriotism,' kind of like what we had with Web defacements during the US-China spy-plane crisis [in 2001]."
Hillar Aarelaid, manager of Estonia's
Computer Emergency Response Team "expressed skepticism that the attacks were from the Russian government, noting that Estonians were also divided on whether it was right to remove the statue". "Today security analysts widely believe that the attacks were condoned by the Kremlin, if not actively coordinated by its leaders." Andy Greenberg, author of the WIRED Guide to Cyberwar 23 August 2019. He noted that the next year, 2008, similar attacks on Georgia were accompanied by a Russian physical invasion.
wired.com. Clarke and Knake report that upon the Estonian authorities informing Russian officials they had traced systems controlling the attack to Russia, there was some indication in response that incensed patriotic Russians might have acted on their own. Priisalu discussed the attack's impact on the Estonian financial system, while Woodcock described the methods the
Estonian CERT used to coordinate defensive actions with network operators and their counterparts in neighboring countries, and Vseviov talked about the broader societal implications of the attack, and
NATO's Article 5 obligations. == Claiming responsibility for the attacks ==