The contents of the messages were unclear.
Responding to an AFP request for comment, the State Department said it was aware of the incident and was “currently investigating the matter”.
“The department takes seriously its responsibility to safeguard its information and continuously takes steps to improve the department’s cybersecurity posture to prevent future incidents,” said a senior State Department official.
The impersonation of Rubio was one of “two distinct campaigns” being probed in which threat actors impersonate State Department personnel via email and messaging apps, the cable said.
The second campaign began in April and involves a “Russia-linked cyber actor” who conducted a phishing campaign targeting personal Gmail accounts associated with think-tank scholars, Eastern Europe-based activists and dissidents, journalists, and former officials, it said.
The cyber actor posed as a “fictitious” State Department official and sought to tap into the contents of the users’ Gmail accounts, added the cable.
‘Malicious actors’
The hoaxes follow an FBI warning that since April cyber actors have impersonated senior US officials to target their contacts, including current and former federal or state government officials.
“The malicious actors have sent text messages and AI-generated voice messages – techniques known as smishing and vishing, respectively – that claim to come from a senior US official in an effort to establish rapport before gaining access to personal accounts,” the FBI said in May.
In May, US President Donald Trump said an impersonator breached the phone of White House Chief of Staff Susie Wiles.
US senators, governors, and business executives received text messages and phone calls from someone claiming to be Wiles, the Wall Street Journal reported.
The breach prompted a White House and FBI investigation, but Trump played down the threat, saying Wiles “can handle it”.
Senior Trump Administration officials have courted criticism for using Signal and other unofficial channels for government work.
In March, then-national security adviser Mike Waltz inadvertently added a journalist to a Signal chat group discussing US strikes in Yemen. The episode led to Waltz’s ouster.
With proliferating AI voice cloning tools – which are cheap, easy to use and hard to trace – disinformation researchers are concerned about the impact of audio deepfakes to impersonate or smear celebrities and politicians.
Last year, a robocall impersonating then-President Joe Biden stoked public alarm about such deepfakes.
The robocall urged New Hampshire residents not to cast ballots in a Democratic primary, prompting authorities to launch a probe into possible voter suppression and triggering demands from campaigners for stricter guardrails around generative AI tools.
-Agence France-Presse
