Meetup has been hit by a DDoS attack that may be linked to an email-based extortion demand demanding $300 to spare the company from being hacked.

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Scott Heiferman, cofounder and CEO of Meetup, wrote on the company's blog that the attack occurred on Thursday; the site has been down several times since then. Heiferman wrote that this was the first such attack in the company's 12-year history:

Here’s what happened. On Thursday morning, I received this email: Date: Thu, Feb 27, 2014 at 10:26 AM Subject: DDoS attack, warning A competitor asked me to perform a DDoS attack on your website. I can stop the attack for $300 USD. Let me know if you are interested in my offer. Simultaneously, the attack began, our servers were overwhelmed with traffic, and our services went down.

Meetup was able to mitigate the attack, but was knocked offline for about 24 hours, he wrote. The site was up again on Friday morning but than was hit with another DDoS attack on Saturday at 4 p.m. ET. After fixing the site Saturday night, yet another attack came on Sunday.

"The natural question I know many of you will ask is why didn’t we pay, especially since the amount of money demanded was ridiculously small?" Heiferman wrote. Meetup doesn't want to negotiate with criminals, Heiferman wrote, and felt the email could have been a trick. Furthermore, the payment could have set a precedent and make Meetup a target for other hackers. Heiferman felt that Meetup could counter the attack.

The attack came shortly after Bitly suffered a DDoS attack last week. The popular URL shortening tool recovered after a few hours. Meanwhile, Heiferman reports that some 60,000 Meetups took place while Meetup.com was down.

The site was still down at the time of writing.