Mobile-phone users worldwide sent 19 billion short message service (SMS) messages to each other in May. Text messaging is cheap, fast and easy, but that ease of use will bring drawbacks, according to Phil Fraher, chief financial officer and chief operating officer of San Francisco-based software firm Brightmail. Mr Fraher foresees an increase in unwanted SMS messages, similar to 'spam' mail which plagues users of the wired Internet. Part of the problem is the default mobile e-mail addresses tend to be the same as subscribers' phone numbers, making it easy for spammers to generate random mailing lists. In Japan, Europe and the Philippines, spam has become a big enough problem for mobile networks and their subscribers to react. In one case at Japan's NTT DoCoMo's i-Mode data service, 'e-mail was sent that automatically triggered the phone to dial an emergency number', Mr Fraher said. 'People's phones were automatically dialling that number every two minutes and they could not turn it off.' DoCoMo responded by boosting the number of addresses users could block to 10 from the previous five, and by helping them change mobile e-mail addresses. 'In the Philippines, there is one company that has actually shut down the entire program for converting e-mail, Mr Fraher said. 'The problem is a lot of that e-mail coming in is junk and converting is costing a lot of money.' Brightmail, which makes software to filter unwanted e-mail, is working with the Philippine company to install software to block e-mail before it is converted. In Europe, SMS is popular for participating in instant polls and requesting instant soccer results. 'Hundreds of thousands of people are signing up for real-time scores sent to their phones during the match,' Mr Fraher said. 'But beware of what you do when you sign up and make sure you tick off boxes that say, 'yes, I would like to receive further notices on products or apparel' or whatever',' he said. Legislation to ban spam was still being considered in the European Union, Mr Fraher said, although he added laws probably would be ineffective at stopping the spread of unwanted text messages. The potential for mobile-phone spam also is unlikely to stop the rapid acceptance of short messaging. As of July, GSM (global system for mobile) networks worldwide had 565 million subscribers. SMS use on these GSM networks more than tripled last year, and might do the same this year. NTT DoCoMo's i-Mode service uses a different network standard, but messaging is among the most popular functions on the service. Apart from spam, mobile users would have to worry about viruses as well, Mr Fraher said. He said the company was watching for viruses because as phones became more technologically advanced and were programmed with software they would become more prone to attack.