Let us hope Department of Homeland Security officials took note of recent remarks by their boss, Jeh Johnson, on a major terrorism threat that requires careful attention.

Speaking to the American Bar Association, Johnson, who heads the department, reviewed various types of terrorism challenges. Indeed, the department has to cope with everything from airline security to what is coming through the nation’s seaports.

But Johnson also said this: “We are concerned about the independent actor, who did not train at an al-Qaida camp, or associate with or take orders from any member of al-Qaida, but who is inspired by al-Qaida’s terrorist ideology – the so-called ‘lone wolf’ who may be lurking within our own society.”

He is absolutely right. Of the 15 or so terrorist attacks on our soil since President Barack Obama took office, all appear to have been conducted by “independent actors.” They range from the Fort Hood shootings to the Boston Marathon bombs.

Clearly, Johnson’s department – working closely with local law enforcement agencies – should view such “lone wolf” attacks as a concern at least as pressing as guarding against another mass assault such as Sept. 11, 2001.