Microsoft Windows is prone to a vulnerability that could let attackers replay NTLM (NT LAN Manager) credentials. A successful exploit would let an attacker execute arbitrary code in the context of the affected user.
Block external access at the network boundary, unless external parties require service.
Configure firewalls to block or ignore unsolicited traffic to ports 139/445.
Run all software as a nonprivileged user with minimal access rights.
Running software as a user with least privileges possible may help mitigate the impact of a successful exploit.
Do not accept communications that originate from unknown or untrusted sources.
Do not attempt to connect to unknown hosts or networks.
The vendor has released advisories and updates. Please see the references for details.