You're listening to the inquiry from the BBC World Service with me

Helena Merriman. Each week we bring you four expert witnesses

answering one pressing question from the news. It's morning on the 27th of June, and Ola deravianco, the head of one of Ukraine's largest cybersecurity companies,

is shopping at his local market.

He's picking up food before a long drive to his parents' house.

He's going to spend some time there with his family. Or so he thought.

At around 11 a.m. he gets a phone call. It's a cry for help. Ukraine is under cyber attack. Within hours, it

spreads, infecting over 60 countries all over the world.

What happened next made history?

The so-called not-petier attack caused more damage than any other previous cyber strike. A few weeks ago, the Intelligence Sharing Alliance known as the Five Eyes,

the US, UK, Canada, Australia, and New Zealand accused Russia of orchestrating the attack.

We saw an indiscriminate attack launched by Russia against the Ukraine, but what they used was a cyber weapon that was launched in the dark and

caused damage to our economies. It stopped shipping from moving. It stopped companies. It literally shut them down and that's just unacceptable.

That was the White House Cybersecurity Coordinator talking to CNBC.

The attack was eight months ago, yet people are still trying to understand exactly what happened.

So in this week's inquiry, with the help of some of the world's leading cyber security

experts, we're going to tell you the story of that attack, how it began and the extraordinary

way in which it spread.

We're asking, what happens when a cyber attack strikes? Part 1, the scene of the crime.

The Scene of the crime.

It was the day before the national holiday and it's summertime, so I was actually taking a day off.

That's Ola de Vivianco, the chairman of ISSP in Ukraine, a cyber security company.

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