Wireless messaging provider Wireless Services said today that 43% of all text messages sent over U.S. networks are spam messages, based on studies of its own network traffic.

The provider said it blocked 1.2 billion spam messages last year, and based on its own estimates of carrying 15% to 20% of U.S. SMS and MMS traffic, concluded that almost half of the messages hitting the network are from spammers. In 2003, spam only accounted for 18% of text messages, meaning spammers have begun focusing their attention on mobile messaging as SMS gains popularity in the U.S., Wireless Services said.

"Everyone hates spam, whether it lands in your e-mail inbox or mobile phone," said Wireless Services CEO Rich Begert in a statement. "But with mobile spam, consumers have to pay for the delivery of annoying, unwanted messages to their personal phone. Even worse, some of the spammers will try to trick you into making an expensive call or will attempt to change the settings on your phone."

Begert said the problem has been exacerbated by the use of anti-spam solutions originally intended for e-mail. Spammers have figured out how to bypass e-mail safeguards when targeting mobile devices, he said.

Wireless Services provides text and picture messaging, mobile e-mail and mobile Internet services to more than a dozen U.S. carriers including Nextel and AT&T Wireless, which is now part of Cingular Wireless.