. >> stahl: mcgahn hired dmitri alperovitch and george kurtz, co-founders of a computer security firm called crowd strike, to investigate. they zeroed in on a suspicious email purportedly sent by a board member to 13 people in the attachment. a few people clicked on an attachment and that let the chinese in. it was sort of like opening the front door. >> stahl: what do you mean, they were in? >> alperovitch: once they clicked on that email and they opened up the attachment, malicious codes started executing on their machine and it beaconed out to the chinese and basically let them right into the company. from that point, they can hop to any machine and take any file that they wanted from that network. >> stahl: by analyzing who the email was sent to, they were able to infer that the chinese were after more than just computer codes. >> alperovitch: they also wanted to figure out the legal strategy of the company, now that they were suing sinovel for $1.2 billion. >> george kurtz: whenever there's a big lawsuit, we'll see the chinese government actually break into that company, break in