They use this advertisments for future use. Making a nation fear that any moment terriost may attack gives them more support for future invasion.
Remember studying the year of the "Yellow Peril", the "red invasion". Well places of interest nowdays are in Muslim lands and since terriosm is common among Muslim exteremist hey use this terriost scare propoganda.
It is also infested in the New's. You will see espically on NBN and Ten when they say a bomb is exploded in Israel they concentrate much on the innocents killed in the attack, but when Israel recently let off a car bomb in Damascus the news only reported the death of the Hamas leader. Yet the footage showed a large area damaged by the bomb including blown up cars. One who is sane would have to believe that many innocents were killed in that attack, but they did not say.
Now to ask why they do this, well Paker is the owner of the NBN and is the richest man in Australia. He also owns many other media outlets along with Murdoch. Both these men gain much through liberal economics they may own large amount of shares in companies that make money from overseas invesment espically after a war (that is Imeperialisor Neo colonalism or the softer word Neo-liberalism). Like oil comapanies or building and earth moving, or may set up factories there.Also the government may give them tax cuts if they are showing the right sort of material that favours them. Many times the Howard government has told off the ABC and SBS and called them bias, eventhough they are public owned and gain not profit from bias. Unlike NBN, Prime and Ten.
So how they government through a liberal economy can control the media without clear signs (like in many other countries that actually plan the media) they can get away with propoganda. Rarelly the public will have a clue and when someone says that is propoganda it is pushed away as a Conspiracy theory. They say things such as "how can it be the government doesnt control the media its private owned". The masses having little or no sense of capitalist economics dont take into account tax cuts, or the owner of the network having shares in companies making profit in Imperialist wars.
With controling the popular stations they then can get the masses with this propoganda. Next time there is a war there will be a large amount of the mass population supporting the war, and will be glad for a war. As they truelly fear a Terriost invasion and believe a pre emptive attacks will prevent this.