how is ddos and dos illegal?

[danielspencer2]

So I was reading that ddos and dos attacks are illegal in the USA,UK and many other countries, but how can the authorities tell whether a person is ddos'ing or just accessing a website lots of times?
For example, if a company had 3000 employees that all went to www.example.com and the website went down, how will the authorities know it was NOT a dos or ddos?

[JRViejo]

danielspencer2, perhaps a review of Wikipedia's Denial-of-service attack might help in answering your questions.

Do read section 2.11 Unintentional denial of service, which would apply to your example.