What are ways to 'harden' yourself as a target for terrorism in terms of 'hardening' personal physical vulnerabilities?
Vulnerability is one of three key ingredients in attack; the others being opportunity and motive. Imagine yourself as a target of a terrorist attack. Examine your personal physical vulnerabilities and develop ways to 'harden' yourself as a target for terrorism.
First of all, we have to realize that “physical vulnerabilities” do not refer to those connected to our own bodies. Terrorism is not, in general, something that you can “harden” yourself against by becoming fitter. That is because terrorism is typically conducted through attacks on masses of people. You cannot “harden” yourself as a target by, for example, lifting weights or becoming a martial artist. No amount of this would be at all likely to help you avoid becoming the victim of something like the 9/11 attacks or the Boston Marathon bombing.
Our physical vulnerabilities, then, revolve around things like our homes and our cars. Even in this case, though, it is hard to talk about hardening ourselves as targets because terrorists are not typically interested in attacking individual homes specifically. Instead, they wish to attack areas with large numbers of people (World Trade Center, London subway system) or symbolic value (World Trade Center, Pentagon). There is little that we can do, then to harden ourselves as individuals.
If we must try to do so, we could conceivably do a few things. We could install bulletproof glass in the windows of our cars and our homes. We could install air filtration systems in our homes and cars that would prevent us from being affected by chemical attacks. We could carry around some sort of gas mask to protect ourselves from some chemical attacks when we are in public. If we live in an apartment building, we could demand that the parking lot be secured and that things like bollards be put in the sidewalks around the building so that suicide car or truck attackers could not ram their vehicles into our buildings.
That said, civilians like ourselves are inherently soft targets and there is little we can do about it.