Vagabond is right.. this wasn't a lack of security issue in the compound but an attack in traffic.. and that's very easy to carry out when the traffic is jammed up as is the case en-route to the airport...
There are security compounds very close to the airport and it might be time for contract companies to re-think the Kabul housing in Akhbar Kahn district.. Another improvement might be to stop using easily identifiable vehicles such as large shiny SUVs and people movers.. I always feel pretty relaxed when being driven by a local driver in an ordinary car.. often with an Afghan scarf around my neck... why try to stand out ?