Smartphone users have today been offered free antivirus and anti-spam software for their handsets - but only for a limited period.

The offer from security firm Trend Micro is only open to devices that use the Windows Mobile 2003 operating system, but a version for Symbian and Pocket PC devices will be out in January.

The software package protects against viruses and SMS spam and needs regular updates. The company said that the offering will be free, but only until July 2005.

"Many people will put hi-tech gadgets, data-centric mobile phones and PDAs on their holiday gift wish-list," said Raimund Genes, president of Trend Micro EMEA.

"As the number of people using the devices increases, so they become more enticing targets for virus writers. By offering the first version of Trend Micro Mobile Security free of charge, Trend Micro wishes to provide its customers and their data-centric devices a secure holiday season."

Last month antivirus companies warned that the Cabir mobile phone virus had been spread for the first time with destructive software as a payload.