The below Palo Alto article gives you lots of good information on how to mitigate this threat.
Also, make sure that your firewall has the following Vulnerability Protection signature enabled and applied to your security rules to prevent exploitation by the EternalBlue exploit.
As for checking the AV signatures (Hashes) for this malware, as @Michael_Zook mentioned, go to https://threatvault.paloaltonetworks.com and type the name Petya in the search box, and it will list all contents for you.
I hope this helps
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