The U.S. Cyber Consequences Unit, a non-profit research institute that advises governments and businesses on the costs of cyber attacks, estimated more modest total losses. They were likely to range in the hundreds of millions of dollars, and unlikely to exceed $1 billion, the group forecast.

HIGH MARGIN BUSINESS

A typical cyber insurance policy will protect companies against extortion like ransomware attacks, which insurers say have spiked in the past 18 months. It would cover the investigation costs and also pay the ransom, according to Parisi.

But there are caveats. Companies that did not download a Microsoft patch issued in March to protect users from vulnerabilities may be out of luck, since many cyber policies exclude coverage in such an instance.

Companies using pirated software are also unlikely eligible for an insurance payout, Kalinich said.

Most cyber insurance policies cover breaches of up to $50 million, with much of the losses related to the interruption of the firms' business, Parisi said. Some policies can cover losses for as much as $500-600 million.

Cyber insurance policies also typically cover the cost of notifying those whose data has been breached, hiring a PR agency to address reputational damage and arranging credit monitoring for those affected, as well as potential legal suits.

It is a high-margin business. Insurer Sciemus, for example, has previously said it charges around $100,000 for $10 million in data breach insurance and as much as seven times that to cover attacks causing physical damage.

Other providers include Allianz, AIG, Chubb and Zurich as well as Lloyds' of London insurers such as Beazley and Hiscox.

DEMAND TO RISE

Even before the weekend attacks, demand in Europe was expected to rise after an EU directive is implemented in mid-2018 requiring companies to notify authorities of a data breach.

With strong competition and uncertainty as to how many of the losses over the weekend were insured, the impact on insurance premiums, however, may be muted.

Insurers are likely to more carefully scrutinize risks they take on as well as how they word policies and exclusions, Kalinich said.

"They will want to pick the companies that are most prepared," Kalinich said. Other firms might be eligible for coverage, but more exclusions may apply, he said.

For example, insurers may seek to deny coverage if companies pay the ransom without contacting their insurers first, he said.

"There are really important intricacies. You could end up losing a couple million dollars." (Additional reporting by Andres Gonzalez in Madrid, Elizabeth Piper in London and Mathieu Rosemain in Paris; Editing by Carmel Crimmins and Mary Milliken)