Obama’s national security team is weighing a range of options in response to the cyberattack on Sony Pictures Entertainment, White House Press Secretary Josh Earnest said.

Earnest told reporters on Dec. 18 that the White House is considering a “proportional response,” warning against speculating about what that may entail.

The Associated Press reports that Obama’s FBI has formally blamed the government of North Korea as being behind the cyberattack.

Earnest said the Obama administration is treating the cyberattack seriously, adding that President Obama has been meeting with members of the military, the intelligence community, and other entities to discuss the incident.

According to the White House and the Pentagon, a cyberattack against the U.S. committed by a foreign country can be considered an act of war.

“There is evidence to indicate that we have seen destructive activity with malicious intent that was initiated by a sophisticated actor.  And it is being treated by those investigative agencies, both at the FBI and the Department of Justice, as seriously as you would expect,” Earnest told reporters.

“It has also been the subject of a number of daily meetings that have been convened here at the White House that have been led by both the President’s Homeland Security Advisor and occasionally by his cyber coordinator,” he added. “This includes senior members of our intelligence community and homeland security officials, military, diplomatic, and law enforcement officials as well.”

Earnest pointed out that the cyberattack on Sony is “being treated as a serious national security matter.”

Members of Obama’s national security team “are considering a range of options,” the White House spokesman said.

Those options may “include cyber retaliation, financial sanctions, and even a boost in U.S. military support to South Korea to send a stern message to North Korea,” U.S. experts told Reuters.

“Another could be to return North Korea to a U.S. list of State Sponsors of Terrorism from which it was removed in 2008, but the effect of any response could be limited given North Korea’s isolation and the fact that it is already heavily sanctioned,” according to the article.