Gigabytes worth of data taken during last month's hack of the Ashley Madison dating website for cheaters has been published online—an act that could be highly embarrassing for the men and women who have used the service over the years.

A 10-gigabyte file containing e-mails, member profiles, credit-card transactions and other sensitive Ashley Madison information became available as a BitTorrent download in the past few hours. Ars downloaded the massive file and it appeared to contain a trove of details taken from a clandestine dating site, but so far there is nothing definitively linking it to Ashley Madison. User data included e-mail addresses, profile descriptions, addresses provided by users, weight, and height. A separate file containing credit card transaction data didn't include full payment card numbers or billing addresses.

Rob Graham, CEO of Errata Security, said the dump also included user passwords that were cryptographically protected using the bcrypt hashing algorithm. That's among the most secure ways to store passwords, because bcrypt is extremely slow, a trait that requires crackers to devote vast amounts of time and computing resources. Still, it's highly likely a large percentage of the hashes will be cracked, given rampant use of weak passwords. That will go a long way to preventing the cracking of even moderately weak passwords, although "1234567" "password" and the other mostly widely used passcodes will likely fall after some time.

Ashley Madison officials have stopped short of confirming the published information was extracted from the breach.

"We have now learned that the individual or individuals responsible for this attack claim to have released more of the stolen data," they wrote in an e-mail to Ars. "We are actively monitoring and investigating this situation to determine the validity of any information posted online and will continue to devote significant resources to this effort. Furthermore, we will continue to put forth substantial efforts into removing any information unlawfully released to the public, as well as continuing to operate our business."

As the screenshot above indicates, the dump contains files with titles including "aminno_member_dump.gz," "aminno_member_email.dump.gz," "CreditCardTransactions7z," and "member_details.dump.gz," an indication that the download could contain highly personal details.

People have already taken to 8chan and other sites to discuss the contents of the data. Their posts unsurprisingly report that many of the names and other identifying information appear to be falsified. AshleyMadison.com claimed it had almost 40 million users at the time of last month's breach. It's

Assuming the download turns out to be authentic, people should remember that it was possible for anyone to create an account using the name and e-mail address of other individuals. That means an entry for a given individual doesn't automatically prove the person was behind it. Still, it would be harder for hoaxters to falsify credit card transactions and member profiles. As a result, the data could prove devastating if used by divorce attorneys, blackmailers, and others. This post will be updated as this story develops.

The full text of Ashley Madison's e-mail is:

Last month we were made aware of an attack to our systems. We immediately launched a full investigation utilizing independent forensic experts and other security professionals to assist with determining the origin, nature, and scope of this attack. Our investigation is still ongoing and we are simultaneously cooperating fully with law enforcement investigations, including by the Royal Canadian Mounted Police, the Ontario Provincial Police, the Toronto Police Services, and the U.S. Federal Bureau of Investigation. We have now learned that the individual or individuals responsible for this attack claim to have released more of the stolen data. We are actively monitoring and investigating this situation to determine the validity of any information posted online and will continue to devote significant resources to this effort. Furthermore, we will continue to put forth substantial efforts into removing any information unlawfully released to the public, as well as continuing to operate our business. This event is not an act of hacktivism, it is an act of criminality. It is an illegal action against the individual members of AshleyMadison.com, as well as any freethinking people who choose to engage in fully lawful online activities. The criminal, or criminals, involved in this act have appointed themselves as the moral judge, juror, and executioner, seeing fit to impose a personal notion of virtue on all of society. We will not sit idly by and allow these thieves to force their personal ideology on citizens around the world. We are continuing to fully cooperate with law enforcement to seek to hold the guilty parties accountable to the strictest measures of the law. Every week sees new hacks disclosed by companies large and small, and though this may now be a new societal reality, it should not lessen our outrage. These are illegitimate acts that have real consequences for innocent citizens who are simply going about their daily lives. Regardless, if it is your private pictures or your personal thoughts that have slipped into public distribution, no one has the right to pilfer and reveal that information to audiences in search of the lurid, the titillating, and the embarrassing. We know that there are people out there who know one or more of these individuals, and we invite them to come forward. While we are confident that the authorities will identify and prosecute each of them to the fullest extent of the law, we also know there are individuals out there who can help to make this happen faster. Anyone with information that can lead to the identification, arrest, and conviction of these criminals, can contact information@avidlifemedia.com.

Post updated throughout to add newly available information.