Speakers at a U.S. Federal Trade Commission hearing on Tuesday said it is difficult to pin liability for the worsening problem of text message spam on any particular group because of the number of third parties in the business.

“These affiliates could be 19-year-old kids in a garage in Paducah, and clearly you need to sue people that your resources can best impact the problem,” said William Haselden, Florida Assistant Attorney General.

The affiliates include aggregators that provide communications gateways between content providers and carriers, firms that provide billing systems, advertising networks, and content providers.

The Florida AG targeted the carriers initially because they get “the lion’s share of the revenues,” Mr. Haselden told an FTC town hall audience.

“But we have also looked at the aggregators, billing aggregators, and advertising networks,” he said. “But you need to deal with the people closest to the subscribers and the carriers are the ones that bill for this.”

Despite the lessons learned on the PC-based Internet, cell phone service subscribers are being bombarded with unsolicited ads for mortgages, erectile enhancers, cheap drugs, and adult content.

Short codes, an opt-in technique used by carriers to manage third party access to subscribers, is proving to be inadequate. Carriers lease the use of short codes for services such as ordering ringtones, TV lotteries, and voting etc. that require the subscribers’ assent.

Messages sent via short codes instead of complete telephone numbers are generally billed at a higher rate.

But the process which is normally handled by multiple specialists such as SMS aggregators, billing specialist, ad networks, and carriers can spring leaks in a number of places.

For instance the short codes can fall into the wrong hands, or the legitimate user of the short codes changes his or her approach, and the result in either case is frequently mobile spam.

“We regulate the process as much as we can but it is difficult for us to monitor changes made by the content provider subsequent to the launch of the campaign,” said Alykhan Govani, business development manager for MX Telecom, a New York City based SMS aggregator.

And many times the perpetrators of text spam are outside the U.S. and frequently out of the reach of carriers, aggregators, ad networks, and U.S. law enforcement.

“International cooperation is the hardest part. We have to convince other countries that text spam is not good for them or us,” Mr. Haselden said. “It is important that we get a handle on this.”