After last week's deadly terrorist attacks in Paris linked to ISIS, the hacking collective Anonymous has declared war on the militant group — and a Silicon Valley startup has fallen in the firing line.

CloudFlare is a service that helps websites stay online in the face of overwhelming traffic. It acts as an intermediary or filter and is a vital protection against DDoS attacks (in which someone sends huge amounts of traffic at a site in an attempt to make it collapse under the weight).

The six-year-old company doesn't discriminate when it comes to picking customers. It has even been accused of protecting dozens websites affiliated with ISIS — and has come under fire from some members of Anonymous as a result.

CloudFlare CEO Matthew Prince has now hit back at his critics, suggesting that Anonymous is being hypocritical, given that many of its members apparently use the service.

"I did see a Twitter handle said that they were mad at us," he told The Register. "I'd suggest this was armchair analysis by kids — it's hard to take seriously. Anonymous uses us for some of its sites, despite pressure from some quarters for us to take Anonymous sites offline."

He added: "Even if we were hosting sites for ISIS, it wouldn't be of any use to us ... I should imagine those kinds of people pay with stolen credit cards and so that's a negative for us."

Prince told The Register that CloudFlare was willing to stop protecting websites if approached through the proper US legal channels, though "more often than not, investigators want him to keep sites up rather than take them down."

In a separate interview with International Business Times, the CEO elaborated on this. "Individuals have decided that there is content they disagree with but the right way to deal with this is to follow the established law enforcement procedures. There is no society on Earth that tolerates mob rule because the mob is fickle."

CloudFlare is worth more than $1 billion, Bloomberg reported in March, and expects to go public in 2017. Prince said the company by then could be worth about as much as Workday — which had a value of $7.8 billion at its initial public offering.

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Anonymous, a loose-knit band of hackers and activists, declared "war" on ISIS after more than 120 people were killed, with hundreds injured, in deadly terrorist attacks in Paris on Friday night that the militant group claimed responsibility for.

Anonymous activists have leaked the Twitter accounts and personal details of people it says are affiliated with ISIS and claimed responsibility for having more than 5,000 Twitter accounts deleted, according to The Independent.

ISIS-affiliated accounts have shot back at the campaign, calling Anonymous "idiots."