"They each bear the hallmarks of terrorism carried out by the so-called Islamic State of Iraq and the Levant," Brennan stated at the Center for Strategic International Studies, commenting on the November 13 Paris attacks and the October 31 Russian aircraft crash.
The recent Paris attacks left at least 132 dead and scores of others injured in the worst terrorist attack on France in recent history.
Russian and Egyptian authorities are still investigating whether the crash of the A321 Russia airliner in Egypt was the result of a terror act or mechanical failures.
Brennan also said that the United States was aware of ISIL's plans to carry out an attack in Europe prior to the November 13 assault in Paris.
"I can tell you that it is not a surprise that this attack was carried out from the standpoint of, we did have strategic warning," Brennan stated, speaking at the Center for Strategic International Studies.
According to him, the US intelligence "knew that these plans… by ISIL [were] underway, looking at Europe in particular as the venue for carrying out these attacks."