
This decision was made based on an assessment of this situation, with the principle of protecting our customer ecosystem overall, firmly in mind.
Given the potential impact to customers and their businesses, we made the decision to make the Security Update for platforms in custom support only, Windows XP, Windows 8, and Windows Server 2003, broadly available for download (see links below). That means those customers will not have received the above mentioned Security Update released in March. We also know that some of our customers are running versions of Windows that no longer receive mainstream support. (For example, to further protect against SMBv1 attacks, customers should consider blocking legacy protocols on their networks). This attack type may evolve over time, so any additional defense-in-depth strategies will provide additional protections.
Customers running anti-malware software from any number of security companies can confirm with their provider, that they are protected. As an additional “defense-in-depth” measure, keep up-to-date anti-malware software installed on your machines.
For customers using Windows Defender, we released an update earlier today which detects this threat as Ransom:Win32/WannaCrypt. For those organizations who have not yet applied the security update, we suggest you immediately deploy Microsoft Security Bulletin MS17-010. Those who have Windows Update enabled are protected against attacks on this vulnerability. In March, we released a security update which addresses the vulnerability that these attacks are exploiting. Customers running Windows 10 were not targeted by the attack today. Additionally, we are taking the highly unusual step of providing a security update for all customers to protect Windows platforms that are in custom support only, including Windows XP, Windows 8, and Windows Server 2003. This blog spells out the steps every individual and business should take to stay protected. Microsoft worked throughout the day to ensure we understood the attack and were taking all possible actions to protect our customers. Seeing businesses and individuals affected by cyberattacks, such as the ones reported today, was painful. Today many of our customers around the world and the critical systems they depend on were victims of malicious “WannaCrypt” software. Microsoft solution available to protect additional products