Ransom:Win32/DoejoCrypt.A is the latest threat to beleaguer vulnerable Microsoft Exchange servers, emerging shortly after Microsoft issued emergency patches in early March for four Microsoft Exchange flaws. The flaws can be chained together to create a pre-authentication remote code execution (RCE) exploit meaning that attackers can take over servers without knowing any valid account credentials. The new family of DearCry, a new ransomware family, has been spotted in Australia, Austria, Canada, Denmark and the U.S.
Source: https://threatpost.com/microsoft-exchange-exploits-ransomware/164719/