On March 5, a "cyber event" interrupted grid operations in parts of the western United States, but the hack was just disclosed to the public a few days ago. As of now, officials are not sure who perpetrated the cyber attack.

The attack marked a somber milestone for the US power sector: the unnamed utility company is the first to report a malicious event that disrupted grid operations.

"According to a cryptic report posted by the Department of Energy, the March 5 incident lasted from 9 a.m. until nearly 7 p.m. but didn't lead to a power outage, based on a brief summary of the electric disturbance report filed by the victim utility," E&E News reported on April 30.

Cyber attacks are a growing risk, experts say. Here's what you need to know about them.

What exactly is a cyber attack?

A cyber attack is more than just shutting down the computer systems of a specified entity. It is defined as "deliberate exploitation of computer systems, technology-dependent enterprises, and networks. Cyber attacks use malicious code to alter computer code, logic or data, resulting in disruptive consequences that can compromise data and lead to cyber crimes, such as information and identity theft."

Technopedia lists the following consequences of a cyber attack:

Identity theft, fraud, extortion

Malware, pharming, phishing, spamming, spoofing, spyware, Trojans and viruses

Stolen hardware, such as laptops or mobile devices

Denial-of-service and distributed denial-of-service attacks

Breach of access

Password sniffing

System infiltration

Website defacement

Private and public Web browser exploits

Instant messaging abuse

Intellectual property (IP) theft or unauthorized access