What services are likely running on ports 21 and 23, which were found open during a port scan?

The services commonly associated with ports 21 and 23 are FTP (File Transfer Protocol) and Telnet, respectively. Port 21 is the default port used by FTP, which facilitates the transfer of files between a client and server. It allows users to upload and download files, making it essential for file management tasks.

Port 23 is mainly utilized by Telnet, a protocol used to provide a command-line interface for communication with a remote device or server. Telnet allows users to log into remote systems over the network, enabling remote management and configuration. However, it's important to note that Telnet transmits data, including passwords, in plaintext, which presents security risks.

Understanding the specific ports and their associated protocols is crucial in network security assessments and testing, as it helps identify potential vulnerabilities and areas that may require hardening or alternative secure protocols during evaluations of networked systems.