An Attacker is person, group or entity that attempts to access, extract, insert, reveal, influence, delete, or disclose another party’s data without prior authorization or permission.
Attackers target individual users and organizations including online services, platforms, enterprises and governments. Often, an attacker may not be detected until there unauthorized activity is well underway and the damage done.
A difference between an attacker and a hacker is that the latter typically uses vulnerabilities and exploits against their target research. An attacker might use any tool at their disposal including destroying physical property to wreak havoc.
"Someone triggered an alarm at our Seattle sales office. The attacker made off with some mobile phones and devices, so we've de-provisioned and wiped those devices from our MDM."