At work. Cranking out source code. Then my old Nokia beeps. Missed call. I brought out the caller ID, and it read
Aargh. Not again.
Someone might call them spams, but I'll rather call them scams. They call you up -- usually with a 03 or 028 number -- but then hang up after one ring. Those who are curious might call back the number, expecting a real person to answer the phone. Instead they'll find themselves greeted by a recorded message, with scams that might cost them more later on.
I won't be surprised that everything is automated, and the scam numbers are probably connected with VoIP DID which can be cheaply purchased. You probably can even buy those "scam-kit" on eBay if you look hard enough. They will just install the software, sign up VoIP deals with voice mail and DID number, click on that big button reads SCAM & EARN $$$, and wait for people to fall into the trap. They can even be operated from overseas, be that Indonesia or Nigeria -- everything just routes through the Internet anyway. It does not cost them anything (besides DID which has a low monthly cost). No wonder it is getting more and more popular.
On Skit's blog and 4 Wise Monkeys there are good coverage on this scam, including the numbers that you can block. However I wonder how effective it is to block those numbers, as it is cheap to dump your blacklisted DID and get another one.
For me, I never bothered to call back if there's a missed call. Too lazy I think, even numbers that have contacts associated with them. SMS me if there's anything important.
Update: If you wish to contribute your thoughts on this scam, please head over to 4 Wise Monkeys Community Forum who is working closely on this issue. I am closing comments here to encourage everyone to head over there.