One important aspect of ethical hacking is privilege escalation, which is often abbreviated as PrivEsc or LPE (and sometimes called Local Privilege Escalation). PrivEsc is when one user illegitimately becomes another. An attacker might try to become another user on a system or the superuser.

The escalation techniques I have learned while studying offensive security have been a real eye opener. I'd go as far to say that anyone working in the defensive security space should be trained in the various ways attackers attempt to break in. It is not always as simple as elevating permissions from a low-level user to the root user (which is referred to as vertical privilege escalation); often PrivEsc means you must first perform horizontal privilege escalation, moving from one non-root user to another. Low-level users often have subtly different privileges or different access to files or scripts that might be more hackable. Attackers move from user to user, looking for the account that offers the best opportunity for escalation.

The Wikipedia page on privilege escalation [1] sums up PrivEsc nicely: "Privilege escalation is the act of exploiting a bug, a design flaw, or a configuration oversight in an operating system or software application [...snip...]. The result is that an application with more privileges than intended by the application developer or system administrator can perform unauthorized actions."

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