Wireless subscribers will top 1.1 billion by 2004, but viruses could threaten the growth of the system. A report issued Tuesday by Allied Business Intelligence, Oyster Bay, N.Y., predicts wireless infrastructure will grow ahead of subscribers to reach nearly 2 million points of presence worldwide in four years. The report comes just as Russia's Kaspersky Lab identified a computer virus that attacks mobile phones. The virus, dubbed ``Timofonica,'' repeatedly sends false e-mail messages to users. Marketers are eyeing mobile phones as a new medium for b-to-b advertising in coming years, as suppliers look for ways to reach customers away from the office.