During a penetration test, you have obtained a low-privileged user shell on a Linux system. You want to perform privilege escalation to gain root access. Which of the following methods would be the most effective initial step in identifying potential vectors for vertical privilege escalation?
Examine the /etc/passwd file for users with a UID of 0
Check currently running processes and services using commands like ps aux, top, or systemctl
Brute-force the root account password using a tool like Hydra
Review all entries in the /etc/crontab for cron jobs that a user may be able to modify