The protocol that most likely allowed the data theft to occur is SMB over TCP port 445. SMB is a network file sharing protocol that enables access to files, printers, and other resources on a network. Port 445 is used by SMB to communicate directly over TCP without the need for NetBIOS, which is an older and less secure protocol. The security log shows that the source IP address 192.168.1.1 sent a file named secrets.zip using SMB protocol to the destination IP address 192.168.1.50, which captured the file. The Windows firewall information shows that port 445 is enabled for inbound and outbound traffic, which means that it is not blocked by the firewall. Therefore, port 445 is the most likely port that was exploited by the attacker to steal the data from the corporate laptop.
Reference:
SMB port number: Ports 445, 139, 138, and 137 explained1
What is an SMB Port + Ports 445 and 139 Explained2
CompTIA A+ Certification Exam Core 2 Objectives3