Researchers Danny Adamitis and Paul Rascagneres said in a blog post that the compromise had been carried out through a new DNS hijacking technique.
In their first report on Sea Turtle, the Cisco researchers said a total of 40 organisations in 13 countries had been compromised by what they claimed was an advanced state-sponsored actor that appeared to be looking to gain persistent access to sensitive networks and systems.
The organisation that manages the top-level domains for Greece is known as the Institute of Computer Science of the Foundation for Research and Technology – Hellas or ICS-Forth announced on 19 April that it had been compromised. Adamitis and Rascagneres said Cisco telemetry had confirmed that Se Turtle was responsible.
"Our telemetry indicates that the actors maintained access in the ICS-Forth network through at least 24 April, five days after the statement was publicly released.
"Upon analysis of this operational C2 node, we determined that it was also used to access an organisation in Syria that was previously redirected using the actor-controlled name server ns1[.]intersecdns[.]com. This indicates that the same threat actors were behind both operations."
New primary targets which were attacked by Sea Turtle included government organisations, energy companies, think-tanks, international NGOs and at least one airport, Adamitis and Rascagneres said.
The Talos researchers did not speculate as to which country might be behind Sea Turtle.