High-level targets around the world are constantly being bombarded by cyber-attacks, according to new research, highlighting the vulnerability of critical infrastructure in this globally connected era.

Attacks that lead to down time can cost more than $6 million per day, and more than $8 million at oil and gas companies, according to research prepared for Mcafee.

In today's economic climate, it is imperative that organizations prepare for the instability that cyber attacks on critical infrastructure can cause, said Dave DeWalt, president and chief executive officer of McAfee.

An attack on critical systems -- such as transportation or energy --- could cause widespread economic disruptions, environmental disasters, loss of property and even loss of life, DeWalt said.

The report, surveyed 600 IT and security executives from infrastructure enterprises in 14 countries were surveyed last September.

More than half of the respondents said their companies had been targeted, and nearly 60 percent said they believed foreign governments are behind attacks on critical infrastructure.

As an example, Michael Assante, chief security officer of the North American Electric Reliability, said the US power grid has been a prime target for foreign entities.

They would be looking to learn, preposition themselves to get a foothold and try to maintain sustained access to computer networks.

The most widely reported form of attack was infection with a virus or malware.

More than half of the executives surveyed said they had experienced large-scale DDOS attacks by organized crime, terrorists, or nation-state actors.

A DDoS attack coordinates legions of computers to visit a targeted website at once, overwhelming its server and leaving the site inaccessible to normal visitors.

Executives say that not only are they in general not prepared to deal with cyberattacks, but that they foresee more attacks, and major ones, in the not so distant future.

The report comes on the heels of the highly publicized attack on Google, and other companies, allegedly originating from China.

The attack announced by Google and identified by McAfee was the most sophisticated threat seen in years making it a watershed moment in cybersecurity because of the targeted and coordinated nature of the attack, said DeWalt.