Cyberspies have a new secret weapon: tainted Microsoft Office files.

A rising number of cyberattacks are taking aim at specific individuals at critical government agencies and corporations ? enticing them to unwittingly open a corrupted Word, Excel or PowerPoint file sent as an e-mail attachment.

Clicking on the file relinquishes control of the PC without the user’s knowledge. The attacker then uses the compromised PC as a base from which to roam the organization’s internal network.

Federal agencies and defense and nuclear contractors are under assault. Security firm MessageLabs says it has been intercepting a series of attacks from PCs in Taiwan and China since November.

“The bad guys know which organizations have data worth stealing and are picking them out one by one,” says Alex Shipp, senior technologist at MessageLabs.

?continued @ USAToday