CompTIA PenTest+ Practice Test

Which command allows opening a shell on a Linux system without needing credentials under certain configurations?

1. ssh

2. telnet

3. rsh/rlogin

4. netcat

The correct answer is: rsh/rlogin

The command that allows opening a shell on a Linux system without needing credentials under certain configurations is the one associated with remote shell capabilities, specifically rsh or rlogin. Both of these commands are part of the remote execution features found in Unix/Linux systems, where they can be configured to allow users to execute commands on a remote machine without requiring a password. In particular, rsh allows a user to log in to a remote system and execute commands there. When configured properly, such as by setting up trust in the form of `.rhosts` files or using Kerberos, rsh can facilitate authenticated access without prompting for a password. This can be helpful in scripting and automation where seamless access between systems is required. Although other options like SSH and Telnet also provide remote access capabilities, SSH is designed to be secure and typically requires credentials, while Telnet is less commonly used today for security reasons. Netcat, on the other hand, is a versatile networking tool that can create TCP/UDP connections and do a variety of things, but it does not inherently provide native shell access like rsh does. Thus, under specific configurations, rsh or rlogin can effectively establish a shell session without prompting for credentials, making it the correct choice in this context