Terrorist Tipoffs and an Evolutionary Arms Race

Josh Marshall at TPM wonders something which I wonder too.  Namely, when we identify things as tipoffs, as suspicious circumstances warranting more investigation, what stops the terrorist organizations from adapting?  For example, John Doe is committed to blowing up an airliner.  So he boards an airliner paying cash for a one-way ticket with no luggage and using a false name.  All sorts of sirens should be going off, right?  But assuming some resources, what's to stop him, knowing what we consider as red flags, from using a credit card, his correct name, and a full set of luggage on a round trip ticket?

And Ann Althouse points to the Newark incident:

"The fact that these two individuals kissed and walked hand-in-hand does not and should not wash away suspicion. If it did, terrorists would know how to stage a security breach. Have male and female confederates. The woman passes through security and then lets in the man, who has whatever weapons/bombs on him that may be desired. The two act like lovers, and the TSA workers sit back and think ain't love grand. A few hours later, hundreds of human beings are blown to pieces."

 Biologists point to arms races in evolution where prey and predators, the eaten and the eater evolve defenses and counters. Maybe that's what we have here.  We come up with a profile of the likely terrorist, the terrorist organization figures out what it is (not a hard job) and how to counter the profile (carry luggage, travel with a female companion, whatever).  A successful attack, or at least one close to success, tells us we need to change the profile and the process continues.