An intruder alarm will be a deterrent, as will stickers saying possessions are marked with a product like 'Smart Water', however if they are determined, they will find a way to get in unfortunately. The best thing is for residents to secure their premises the best way they can I guess, ensuring alarms are switched on etc. the best thing we can do as fellow residents is keep an eye out for any suspicious behaviour and notify the police immediately, also if you hear an alarm, don't ignore it (I am certainly guilty of it in the past), call the police and let them know where it is going off.