FastMail has been subjected to a number of distributed denial of service (DDoS) attacks, the premium email provider has revealed.

The Australian-based company said that the cyber offensive first took place in the early hours of November 8th, which took some of its services offline.

In response it immediately “enabled mitigation strategies”, which proved successful in bringing the DDoS attack to an end.

However, the following day, at around the same time, the cybercriminal once again launched another onslaught.

This second-round of attacks came with a ransom demand, which threatened FastMail with more chaos if it didn’t hand over 20 Bitcoins (worth approximately £7,500).

The company said that it does not respond to attempts of extortion and will not bow to pressure from the cybercriminal.

“Over the last week, several email providers, including Runbox, Zoho, Hushmail and ProtonMail have been hit by large scale DDoS attacks, accompanied by an extortion demand from the attacker to stop,” FastMail outlined.

“The goal of the attacker is clearly to extort money in the hope that the services will not be prepared to deal with the disruption.

“With one exception, where ProtonMail paid the criminals and was still attacked, we do not believe the extortion attempts have been successful, and we fully intend to stand up to such criminal behaviour ourselves.”

"We have preparations in place for mitigating various other DDoS scenarios, and are ready to adapt to whatever form of attack might come through."

The company says that it is actively working to keep its services running as best as possible and that it has utilized knowledge gained from past DDoS attacks to help it react to numerous situations.

The attack on ProtonMail is one of the most high-profile cases of 2015, which the encrypted email provider has described as the “largest and most extensive cyberattack in Switzerland”.

A DDoS attack is when numerous computers make repeated requests for information to one computer or device.

This has the effect of ‘overwhelming’ a computer or device’s ability to deal with the requests, resulting in it slowing down or crashing.