The IRS and industry action groups have warned employers about spear phishing emails. These messages appear to come from an individual (usually high level individual) at a company, but are really masked addresses from a nefarious source.
The messages typically ask the recipient to supply personal information about an employee or transfer sums of money. Companies should warn their workforce about spear phishing scams, and IT departments should be on alert for the messages. Tips from the IRS on spear phishing can be found here.