Already a subscriber? Make sure to log into your account before viewing this content. You can access your account by hitting the “login” button on the top right corner. Still unable to see the content after signing in? Make sure your card on file is up-to-date.

A former top US military official, Retired Gen. Frank McKenzie, the ex-commander of US Central Command (CENTCOM), has sounded the alarm over the danger of online radicalization by ISIS, suggesting it could lead to future terrorist attacks.

This warning comes in the wake of a terror attack in Moscow, where four gunmen affiliated with ISIS-K, the Afghanistan branch of ISIS, killed 144 people at a concert hall. The attackers, originating from Tajikistan, along with their presumed collaborators, have been detained by Russian authorities.

In an interview on ABC, McKenzie said the evolving threat posed by ISIS is mainly through the means of online radicalization. “Self-radicalization — radicalization in place, if you will, by people who have access to the internet abroad — may be one of the most dangerous methods that ISIS can use to generate attacks. Those attacks are generally not going to be well coordinated. They’re not going to be well planned. And they’re not going to be well supported. But they can be very lethal, because there’ll be so hard to detect.”

The Moscow attack has reignited fears of a possible resurgence of ISIS, with concerns that Europe or the United States could be future targets from individuals inspired by the Moscow attack. Despite these apprehensions, American intelligence and the Department of Defense remain vigilant. Pentagon Press Secretary Pat Ryder said, “The Department of Defense has not taken its eye off of ISIS.”