"I believe that if we're not going to put troops on the ground, then we've got to use our Special Operations Forces to go in and collect intelligence; also be able to capture people that might be able to be helpful," she said Sunday on "This Week."
Feinstein added that she is "very worried" about the Islamic State and its spread to at least 12 countries around North Africa and the Middle East.
According to U.S. officials, the Army's elite Delta Force unit killed Tunisian Abu Sayyaf, a senior ISIS leader involved in the group's illicit oil and gas trade, in an attempt to capture and interrogate Sayyaf about hostages and the terror group's finances.
While Sayyaf was killed in the operation -- fighting was so intense that hand-to-hand combat was involved, according to one U.S. official -- American commandos successfully captured the ISIS leader's wife, and rescued a Yazidi woman who appeared to be the couple's slave, according to the National Security Council.
On the continuing strength of ISIS, Feinstein called the group "organized" and "an impressive fighting force."
"It occupies territory. It runs a government. And most importantly it is evil. It annihilates in the most brutal of ways," Feinstein said. "And so I think that we have to get very serious about what we're going to do not only to contain but to eradicate this force."