Two of the most vulnerable operating systems for handhelds are the Palm OS and Microsoft Pocket PC.
The reason they are vulnerable is that they have significant market share, run executable code, and are being integrated into new smart phones.
This makes them attractive and likely future targets for creators of malicious software.
Now is the time to consider protecting your handheld against viruses and worms.
Look for antivirus software that you can update easily and that comes from a reputable company.
Symantec and F-Secure have both released software for handhelds, and other vendors are sure to follow.
Antivirus software costs around $40, works well, and helps prevent malicious code from spreading to your network via your PDA.