[link|http://www.theregister.co.uk/2004/08/05/pocketpc_trojan/|The Register]:

Russian virus hunters Kaspersky Labs have detected a Trojan horse programme capable of infecting PDAs running Microsoft's PocketPC operating system.

Although a very small number of PocketPC viruses have been located, Brador-A is said to be the first backdoor program capable of infecting handhelds running PocketPC. Previous PocketPC viruses have been written as experiments in coding not for malicious intent. Brador-A breaks this pattern by coming pre-loaded with a series of malicious routines.

Now, who would have thought Microsoft's PocketPC was vulnerable?