Former Amazon.com Inc. cloud executive Charlie Bell said he has joined Microsoft Corp. to lead a newly formed role overseeing cybersecurity operations. Bell, who will start as an executive vice president, indicated in a LinkedIn post that his role will include dealing with digital fraud, ransomware attacks and with public exposure of private data. Bell’s appointment comes at a time when Microsoft has been hit hard in terms of cybersecurity shortcomings. Last week, the company warned some of its Azure cloud computing customers that a major flaw discovered by security researchers could have allowed hackers access to their data. In late August, security experts at Wiz described a database flaw that also would have allowed one customer to alter another’s data in the Azure cloud platform. Bell, who long reported to former Amazon Web Services chief Andy Jassy and oversaw the engineering teams working on AWS’s main software services, will …