A penetration tester is performing a port scan on a particular host. The tester discovered multiple ports open, which made determining the Operating System (OS) version installed confusing. Considering the NMAP result below, which of the following is likely to be installed on the target machine by the OS? NMAP 5.21 was launched on March 15, 2011, at 11:06 a.m. The NMAP scan report for 172.16.40.65 Host is now available (1.00s latency). Not depicted: 993 ports have been closed. SERVICE OF THE STATE OF PORT 21/tcp open ftp 23/tcp open telnet 80/tcp open http 139/tcp open netbios-ssn 515/tcp open 631/tcp open ipp 9100 MAC Address: 00:00:00:48:00D:EE:8

The ports that are open are:

- 21/tcp: This is the port for the File Transfer Protocol (FTP). FTP is a standard network protocol used to transfer files between computers. However, FTP is not commonly used by printers.
- 23/tcp: This is the port for the Telnet protocol. Telnet is a network protocol that allows users to connect to a remote computer and control it as if they were sitting at the keyboard. However, Telnet is not commonly used by printers.
- 80/tcp: This is the port for the Hypertext Transfer Protocol (HTTP). HTTP is the protocol used to transfer web pages between web servers and browsers. However, HTTP is not commonly used by printers.
- 139/tcp: This is the port for the NetBIOS-SSN protocol. NetBIOS-SSN is a protocol used to provide network services, such as file sharing and printer sharing. Printers often use NetBIOS-SSN to share their services.
- 515/tcp: This is the port for the Line Printer Daemon (LPD) protocol. LPD is a protocol used to print files to a printer. Printers often use LPD to receive print jobs.
- 631/tcp: This is the port for the Internet Printing Protocol (IPP). IPP is a protocol used to print files to a printer. Printers often use IPP to receive print jobs.
- 9100/tcp: This is the port for the JetDirect protocol. JetDirect is a protocol used by printers to communicate with print servers. Printers often use JetDirect to receive print jobs.

The MAC address that you provided is a common MAC address for printers.

Therefore, the most likely operating system installed on the target machine is a printer operating system.