Phasing out SMB1? Its time to consider

July 7, 2017

Being a business owner, one can probably deal with one machine infected by virus/ransomware. What if ALL the machines in the company are down? No one would want this happen to his/her business.

In April 2017, the Shadow Brokers posted 5th leak, which includes tools and exploits developed by NSA. In less than 3 months, we saw outbreaks of WannaCry ransomware and Not Petya wiper, both caused considerable damages. These malware have one thing in common -- they use vulnerabilities in SMB1 to propagate.

According to Microsoft TechNet, "SMB1 has large number of commands and subcommands, the protocol was also difficult to extend, maintain and secure." Fortunately, Microsoft has introduced SMB2/SMB3 to address these issues. Since majority of (up and running) Windows systems support SMB2/SMB3, administrators should consider phasing out SMB1 entirely to increase network security.

If you are running Windows Server 2008/2013/2016, or Windows 7/8/10 -- you can follow Microsoft's instructions to disable SMB1. (Disabling SMB2/SMB3 is not recommended.) If you are running Windows Server 2003 (and prior), or Windows XP (and prior) -- SMB2/SMB3 is not supported by these operating systems. You should upgrade your systems as soon as possible.

SonicWall customers can also use the following signatures to create policies to restrict SMB1 usage:

  • App Control Advanced sid:5181 "SMB -- Outbound Traffic"
  • App Control Advanced sid:9400 "SMB -- Inbound Traffic"