revelations about a growing terror threat to america that 24 hours ago most of us didn't even know existed. >> it's called the khorasan group and being considered a bigger threat to security than isis. so much so that the group was among the targets hit in monday night's air strikes in syria. abc's brian ross has the latest. >> reporter: a concern was so great that the u.s. dedicated eight of its 22 air strikes against the syrian base of the khorasan group outside aleppo. >> we believe the khorasan group was nearing the execution phase of an attack in europe or the homeland. >> reporter: three key factors about why the khorasan group is considered so dangerous. it's made up of 50 seasoned al qaeda fighters. many of whom who close to osama bin laden. they were building bombs undetectable by the latest airport screening machines. among their targets were passenger jets bound for the u.s. using western recruits posing as tourists to carry the