LONDON, July 25 (Reuters) - Global insured losses from

last week's massive IT outage are likely to range from $400

million to $1.5 billion, cyber analytics firm CyberCube said on

Thursday.

A software bug in cyber security firm CrowdStrike's ( CRWD )

quality-control system caused the software update that crashed

computers globally, the U.S. firm said this week, as losses

mount following disruption to services from aviation to banking.

The outage may be the single largest cyber insurance loss,

CyberCube said in a statement.

It was "a major event for the cyber insurance market but

does not come close to the destructive potential that leading

insurers are holding capital against", CyberCube said.

Insurer Parametrix this week estimated insured losses from

the outage of $540 million to $1.08 billion for Fortune 500

companies, excluding Microsoft ( MSFT ), whose computer software

was affected by the CrowdStrike ( CRWD ) bug.

Major cyber insurer Beazley said this week it had

no plans to change its guidance on its combined ratio - a key

measure of underwriting profitability - after the outage.

The global insurance and reinsurance industry is likely to

avoid any major financial impact from the outage, ratings agency

Fitch said.

However, reinsurance broker Guy Carpenter said that insurers

may face claims on directors and officers' and property

insurance as a result of the outage, in addition to cyber

insurance claims.