I was surprised to see this job add I have to say, ASIO openly advertising for people to intercept transmissions on the new next "G" network. ahh
well, at least it pays well. ASIO Advertisement
You'll find that ASIO advertises positions regularly, no different to any other government agency.
When i was living in Canberra they would particularly target students at the ANU with their position vacant advertisements.
Defense Signals and ASIS are alot more secretive with their recruitment.