Site owners are subject to extortion

Today, a client wrote to the support of our company with the question “What should we do next?” And attached an anonymous letter. The client uses the hosting service.

> Today - 02/13/10 at 15:00 Your site will be exposed to DDoS attack.
> If you want your website to work, pay 30,000 rubles to Yandex
> wallet XXXXXXXXXXXXXXX. In the notes write the address of the site that would be
> could quickly turn it on.
> No need to write in Yandex with the requirement to block the wallet, he
> created individually for you, if it is blocked, we will strengthen the attack.
> The sooner YOU make the payment, the faster your site will work.
> Now the attack will be indicative and not very strong, because and such
> power will be enough to understand the seriousness of our intentions.
> If you try to organize protection against ddos, you have nothing
> it turns out, we have the opportunity to strengthen the attack to such an extent that it does not
> no one can handle! From the attack of 70,000 Russian bots there is no defense! Such
> the attack will not be able to hold even the whole Data Center.
> No need to respond to this email, nobody reads this mail. We will
> check wallet XXXXXXXXXXXXXXX and as soon as it appears 30 000r. from
> You, the attack will stop.

So far, our Cisco Guard is handling it, although the load is felt. But that is not the question.
')
What does our esteemed community think about this? What are the options for fighting extortionists in technical and legal terms?
It is also interesting that Yandex can offer anti-fraud through their service.

UPD: Found a similar post. As you can see the price has tripled since then, i.e. criminals at large.
habrahabr.ru/blogs/infosecurity/68131