LONDON US Fortune 500 companies, excluding Microsoft, will face US$5.4 billion in financial losses from the recent CrowdStrike outage, insurer Parametrix said on Wednesday.

CrowdStrike's faulty update to its security software crashed computers powered by Microsoft's Windows operating system, disrupting internet services across the globe and affecting a broad swathe of industries including airlines, banking and healthcare.

Insured losses from the outage will likely total US$540 million to US$1.08 billion for the Fortune 500 companies, Parametrix said in a statement.

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 mass IT outage.

The global insurance and reinsurance industry is likely to avoid any major financial impact from the outage, ratings agency Fitch said on Monday. 

  - Reuters