Hackers who attacked a U.S. employee of Ethiopian Satellite Television in 2013 have recently launched a new round of attacks against the broadcaster, an Internet watchdog group said in a report published Monday that links the spyware to the Ethiopian government.

Citizen Lab, which is based at the University of Toronto's Munk School of Global Affairs, says the hackers used upgraded espionage software to send out booby-trapped emails in November and December.

The broadcaster's general manager, Neamin Zeleke -- one of those targeted by the malicious messages -- says it didn't take a genius to figure out the same actors were at work.

"They didn't even bother to change the email address," he said.

Zeleke believes Ethiopia's authoritarian government -- one of Africa's top jailers of journalists -- is behind the hackers. He said it was part of a broader campaign of "threats, intimidation and cyberattacks" designed to stifle independent reporting outside the country. According to Human Rights Watch, at least 38 journalists have been charged under terrorism laws or the criminal code since 2010 -- and 60 have been forced into exile over the same period.

"They want to know who is sending us information," Zeleke said. "They will cut off our oxygen, which is information from inside the country."

Ethiopian officials have previously denied such claims, but Citizen Lab said it linked the spyware to the Ethiopian government, citing Internet protocol addresses traced to Ethiopia Telecom, the country's state-run carrier, among other forensic clues.

The electronic messages -- which carried suspicious-sounding asides such as "please note I have temporarily changed my email to this one" -- may have been clumsy but the espionage software they carried was not. Citizen Lab identified the program as a product of Hacking Team -- an Italian company that specializes in spyware geared to law enforcement and intelligence agencies.

Hacking Team spokesman Eric Rabe did not immediately respond to a written request for comment on the report. The Ethiopian Embassy in Washington did not immediately return messages seeking comment. Neither did the FBI's Washington field office.