The terrorist networks of ISIS and al Qaeda are being dismantled but are far from dead, top officials are warning Wednesday, and the threat of a U.S. attack by a homegrown lone wolf has been elevated going into to Christmas.

“We assess there is currently an elevated threat of [homegrown] lone offender attacks by ISIS sympathizers, which is especially concerning because mobilized lone offenders present law enforcement with limited opportunities to detect and disrupt their plots,” according to Robin Taylor, acting deputy under secretary for intelligence operations at Homeland Security.

At a Senate Homeland Security and Governmental Affairs Committee hearing today, Taylor will also warn that al Qaeda [AQ] and ISIS are still terror threats despite losing power recently.

In testimony provided to Secrets in advance, he said that the “core” al Qaeda “and its affiliates remain a major concern for DHS. Despite the deaths of many AQ senior leaders, the group and its affiliates maintain the intent, and, in some cases, the capability to facilitate and conduct attacks against U.S. citizens and facilities. The group and its affiliates have also demonstrated that capability to adjust tactics, techniques and procedures for targeting the West.”

List of officials testifying at today's Senate Homeland Security and Governmental Affairs Committee hearing.

He then turned to ISIS.

“Likewise, we continue to monitor the evolving threat posed by ISIS. ISIS fighters’ battlefield experience in Syria and Iraq have armed it with advanced capabilities that most terrorist groups do not have. Even as the so-called ‘caliphate’ collapses, ISIS fighters retain their toxic ideology and a will to fight. We remain concerned that foreign fighters from the U.S. or elsewhere who have traveled to Syria and Iraq and radicalized to violence will ultimately return to the U.S. or their home country to conduct attacks,” he said.

Protecting the homeland from those attacks has been a key focus of committee Chairman Sen. Ron Johnson. The Wisconsin Republican has held 10 recent hearings on the issue and Johnson said that he plans to keep his eye on the evolving threats as they target the U.S.

“The strategies of a global Islamist jihad have shifted over the past half century to adapt to the changing international landscape and our homeland defense must adapt as well,” said Johnson, according to his planned opening statement.

He said he called Wednesday’s hearing to look into the cyber threat from the groups.

“Military victories over ISIS in recent months have reduced its territorial control in Iraq and Syria by over 95 percent from its 2014 peak. While these victories are worth celebrating, the enemies we defeated in Raqqa are exploiting the frontier of cyberspace. There they seek to leverage social media to recruit vulnerable minds to carry out attacks on their behalf. This is the new phase of the threat facing our homeland,” said Johnson.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com