Account compromise

Definition
Account compromise is

"the unauthorized use of a computer account by someone other than the account owner, without involving system-level or root-level privileges (privileges a system administrator or network manager has). U.S. CERT, "Security of the Internet" (full-text)."

Overview
"An account compromise might expose the victim to serious data loss, data theft, or theft of services. The lack of root-level access means that the damage can usually be contained, but a user-level account is often an entry point for greater access to the system."