New attacks, and taking risk measurement personally

Today, a terrorist used a bulldozer as an attack weapon, running over several cars in Jerusalem, and killing at least three people and wounding many others. It's a novel attack method - the Israeli police and army have gotten quite good at stopping car bombs by preventing them from getting into Israel, but this is a weapon that's already present (and the terrorist was an authorized user of the vehicle, although obviously not for that purpose).

While not taking away from the tragedy of the people killed, or the crime by the terrorists (including their sponsors who are perversely cheering these murders), it's important as security engineers that we're always aware of attacks that don't follow our "script". That's as true for real-world ("kinetic") attacks as for cyber attacks.

More to the point, this attack made me think about risk. My son is in Israel, and his plans are to go to Jerusalem tomorrow - probably even going past the very place where the attack occurred. Should I let him? What are the risks of another terrorist attack? How do those risks compare with the risks that would ordinarily be present in a city - the risk of getting hit by a car while crossing the street? Ultimately, I decided that the risk of another terrorist attack is fairly small in comparison with other risks.

(Incidentally, there's very little non-terrorist violent crime in Israel, so I don't worry about him getting mugged walking around the streets even at night - something I might be more cautious of in an American city.)

Like all parents, I worry when my kids are out driving late at night (even though I don't believe they drink, there's always other drivers to worry about, as well as the fact that they're not very experienced drivers), when they travel, etc. My older daughter is spending the summer in Pittsburgh - and like any big city, there's some amount of street crime there. How much should I try to protect her? (Both my son and older daughter are old enough that I have no legal control, just a parent's moral influence.) Figuring out which risks to allow them to take and which to prohibit is one of the hardest things about being the parent of young adults.