PT0-002 Exam Dumps - CompTIA PenTest+ Certification Exam

"A significant issue identified by Wiberg is that using active network scanners, such as Nmap, presents a weakness when attempting port recognition or service detection on SCADA devices. Wiberg states that active tools such as Nmap can use unusual TCP segment data to try and find available ports. Furthermore, they can open a massive amount of connections with a specific SCADA device but then fail to close them gracefully." And since SCADA and ICS devices are designed and implemented with little attention having been paid to the operational security of these devices and their ability to handle errors or unexpected events, the presence idle open connections may result into errors that cannot be handled by the devices.

The VRFY and EXPN commands can be used to enumerate user accounts on an SMTP server, as they are used to verify the existence of users or mailing lists. VRFY (verify) asks the server to confirm that a given user name or address is valid. EXPN (expand) asks the server to expand a mailing list into its individual members. These commands can be used by a penetration tester to identify valid user names or e-mail addresses on the target SMTP server.

 The commands are used to clear the Bash history file of the current user, which records the commands entered in the terminal. The first command redirects /dev/null (a special file that discards any data written to it) to temp, which creates an empty file named temp. The second command changes the timestamp of temp to match that of .bash_history (the hidden file that stores the Bash history). The third command renames temp to .bash_history, which overwrites the original file with an empty one. This effectively erases any trace of the commands executed by the user.