FYI, hackers are doing a lot of SMS spam which I found out the hard way last year when one of my email servers got compromised and was being used to send about 600K spams when I caught it. The messages are much smaller so they can send a ton and they don't even have to relay it as a prefix spammer script can be installed. Think war dialing technology. This masks the actual source of the spam as the script on your server is just cranking out spams to sequential phone #s.
The only upside is it wasn't sending spam to real email addresses and it didn't get caught by any of the spam trackers out there and didn't show up on any RDNSBL services I checked (100+), therefore the IP address wasn't compromised when I got the problem resolved.
The downside is it's obvious these big phone companies aren't sharing this spam data, if they even spotted it in the first place, and servers compromised for SMS spamming may go undetected by the rest of the community, or even the server's owner. I wouldn't have noticed myself except the load of 600K spams in the outbound queue caused an unusual CPU load on the dual quad-cores in that box so I knew something was wrong. Had they throttled their delivery to something lower it could've gone undetected for days, if ever.
Thank goodness they're greedy!