When the World Wide Web became widely available that same decade, viruses, worms and malware became problems in e-mail accounts, frustrating users who clicked on messages thought to be legitimate.

CNN: Facebook, Twitter crooks just a click away

Security analysts say they've already seen all of the major online threats -- Trojan horses, viruses, worms -- spreading on smartphones, often through e-mail attachments sent to the phones.

CNN: Smartphone security threats likely to rise