Legacy - filtered SMB ports?!?


I am brand new to HTB and pen-testing in general.

I am working on the Legacy box right now, and am super confused.

When I do an initial Nmap scan, ports 139 and 445 are open.

I’ll do another scan like 20 minutes later, and they will come back as “filtered”. WTF is going on?

Had the same problem after running an exploit for the wrong Service Pack version. Resetting the machine fixed it.

Hello, having this same exact problem… I reset and switched to EU VIP access with new connection package… Nothing is working, they’re all port filtered…

On that note, how do you guys fingerprint the OS? MSF’s ‘smb-fingerprints’ is able to nicely identify the operating system, language, and service pack. Whereas nmap’s smb-os-discovery script only reported that the machine runs either XP or Server 2000.
Should not be a rocket science to adopt MSF’s method into standalone script, but I am wondering if there is something already out there that can produce better results than the mentioned script.