Check if the AV vendor has released a signature or emergency signature for the new malware. Ensure all the systems have this new signature. Run regular reports to make sure 100% of systems and servers are compliant.
Identify the IOCs (File hashes, URLs and mail address involved, IPs). Use these IOCs in all possible devices (Firewall, Proxy, internal TI, etc)
Feed the IOCs in to SIEM and configure rules to trigger if any of the IOCs appear in your network.
Research on the malware and see if it is targeted to a specific vertical or region.