Smartphones, like computers, are vulnerable to hackers. So far the threat has been low, but as users start to use their smartphones more and more as mobile computers the risk will increase, according to the Wall Street Journal [Subscription Required] on Tuesday. Corporations are thinking more and more about the possible problems.

As a result, IT departments are starting to restrict access to their internal networks.

One reason is the popularity of smartphones thanks to the Apple iPhone. While smartphones comprise only 17 percent of the total market, their use is up 10 percent in one year. To date, the threat has remained low, and there are less than 500 known viruses for all phones [and none specifically for the iPhone], that work mostly through attachments or Bluetooth. Even so, companies with smartphone access to their networks are planning proactively.

One reason the threat is low right now is that, unlike Windows, a dominant OS hasn't yet emerged. Symbian has 65 percent of the market share and Windows mobile 11 percent. "It's very inefficient to write a virus for phones," said Nick Magliato, CEO of Trust Digital, a security vendor.

The major threats include unauthorized network access to private corporate data, through either snoopy viruses or malicious applications that aren't digitally signed by a vendor, the transfer of malware into the corporate network, or the outright loss of the smartphone that contains sensitive corporate data. That's why most corporations insist on a mechanism to wipe a smart phone clean remotely if it's lost or stolen.

iPO notes that it's been almost a year since the Apple iPhone was released, and there have been no known incidents like those cited above. Apple, with its recent enterprise initiatives, and its corporate customers are trying to keep it that way.