Card-payment processor Authorize.Net, which provides an Internet gateway for credit- and debit-card authorizations on behalf of 100,000 merchants and their online shopping customers, last week suffered a crippling distributed denial-of-service attack for several days from an unknown source.

The distributed DOS attack, which disrupted Authorize.Net’s payment processing and strained the resources of its customer support center, was reduced to an intermittent network delay by last Wednesday. Lightbridge Inc., which owns Authorize.Net, received a demand for money associated with the distributed DOS attack, said spokesman Glenn Zimmerman.

While Lightbridge was not at liberty to provide details about the possible attackers or the extortion because it is working with the FBI to investigate the crime, Zimmerman said the firm did not bend to the attacker’s demands for money. Lightbridge said it will also quickly be deploying technologies aimed at mitigating distributed DOS attacks.