Hackers are exploiting old holes in Microsoft applications again: this time they've found a way to take over computers through some older versions of Excel. 

Microsoft hasn't yet decided whether to patch the hole.
Apparently, the flow works if users open a specific Excel attachment, or visit a malware Web site. This would allow the malware to retreive information from their PC, or add it to a bot network.
The hole is only found in older versions of the spreadsheet software, and the latest versions are not affected.