Symantec and McAfee are expanding their mobile security services as malware writers step up their attacks on mobile devices. 

Symantec unveiled its Mobile Security Suite 5.0 on Tuesday which promises to protect mobile phones running Windows Mobile.

The bundle includes antivirus software, firewall, SMS spam filter and data encryption technology. The company currently only offers a mobile antivirus product.

Smartphones and other mobile devices are commonly exposed to insecure Wi-Fi networks as well as applications that users download and install from the internet. But they also connect to corporate networks and client computers.

Malware writers are warming up to the possibilities of mobile malware, Symantec warned. Research from the security vendor has indicated that the number of mobile viruses doubles every six months.

Symantec expects to start shipping its mobile security suite by May, but did not release pricing information. Symantec unveiled its new offering at the CTIA Wireless show in Orlando.

At the same event, McAfee released the McAfee OK program which inspects and certifies mobile content at the operator and network aggregators before it is transmitted to consumer's handsets.

The software offers to inspect ring-tones, images, video and applications, and is based on McAfee's existing mobile detection technology for the Symbian mobile operating system.