![]() ![]() Download the Microsoft Safety Scanner (MSERT) tool and scan for potential open Web Shell connections to your Exchange Server(s) for these four zero-day vulnerabilities.Disable Outlook Web Access and related public-facing ports.Reset all users’ Active Directory passwords with an Exchange mailbox.Short-term “Defense”: Patch, Block Ports and Change Passwords Time is of the essence and action must be taken immediately to protect your data. Tens of thousands of companies are at risk in the US and internationally. However, widespread attacks by Hafnium (rumored to be state-run) have taken advantage of four previously unknown vulnerabilities in Microsoft’s “on-premise” versions of Exchange Server. ![]() Typical zero-day attacks usually take place using a single vulnerability. ![]() In this case the attacker was using one of the zero-day vulnerabilities to steal the full contents of several user mailboxes from such servers. Microsoft Exchange Server is software that offers this functionality for Windows-based server systems. In many organizations, internal cooperation depends on groupware solutions that enable the central administration of emails, calendars, contacts, and tasks. Exchange Server is primarily used by business customers, and we have no evidence that Hafnium’s activities targeted individual consumers or that these exploits impact other Microsoft products. We strongly encourage all Exchange Server customers to apply these updates immediately. Today, we released security updates that will protect customers running Exchange Server. We’re focused on protecting customers from the exploits used to carry out these attacks. ![]() Third, it would use that remote access – run from the U.S.-based private servers – to steal data from an organization’s network. Second, it would create what’s called a web shell to control the compromised server remotely. First, it would gain access to an Exchange Server either with stolen passwords or by using the previously undiscovered vulnerabilities to disguise itself as someone who should have access. Hafnium has engaged in a number of attacks using previously unknown exploits targeting on-premises Exchange Server software.The attacks included three steps. Microsoft attributes the attacks to a group they have dubbed Hafnium. Microsoft has detected multiple zero-day exploits being used to attack on-premises versions of Microsoft Exchange Server in limited and targeted attacks. ![]()
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