(UPDATED) Alternative payment provider Dwolla has been hit by a distributed denial of service attack that took the company's website down for a period of time yesterday. The website is back up but a post on the company's blog said issues persist due to the attack.

No details have been provided at this time on why Dwolla was targeted or by whom, but the company said it is notifying third-party developers who use the service for sending and receiving funds as well as working with service providers to fix the situation.

The last update to the Dwolla blog from late Thursday afternoon said the company has made "meaningful progress" with service providers and is beginning to test accessibility with its web application. It promised testing of the API and mobile application would take place soon.

Needless to say, Dwolla customers are less than happy with the situation, with many posting comments to the company's blog demanding answers on when the situation will be rectified and questioning Dwolla's contingency plans.

"Has anyone developed a disaster recovery plan?" asked one commenter. "[T]his should have been factored in when you started your business. I have a lot of money sitting in my account that I need to pay my contract workers with. If you're going to handle money, your system needs to be bullet proof!"

What makes the outage particularly difficult for some account holders is that they use Dwolla to buy bitcoins, the virtual currency, through bitcoin exchanges like Mt. Gox. Thanks to currency troubles in Cyprus, bitcoins have seen a steep rise in their value. Several commenters on the Dwolla blog expressed frustration that inability to buy bitcoins has kept them from taking advantage of that rise. 

Meanwhile, Dwolla employees are providing information as it becomes available and the company has been upfront about its issues. Even company CEO Ben Milne has joined in moderating comments on the company blog, at one point finishing a post with the understated hashtag #lessthanidealmorning.

More updates as they become available.

UPDATE: According to Dwolla's blog, the company's API is back up and running as of 1:05 CT. 

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