Who hacked Ashley Madison
An estimated 37m Ashley Madison website users' information has been leaked (Reuters)

Hacked adultery website Ashley Madison has been attempting to control the leak of information of its 37 million users by issuing copyright infringement notices to several websites and forcing the deletion of tweets.

In the days after the leak of private information from the website, which allows users to have an affair, several sites popped up that allowed people to enter an email address to see if their details were included in the large data dump.

However, some of these sites, including CheckAshleyMadison.com and AshleyMadisonLeakedData.com, now no longer allow users to check their details after being sent copyright infringement notices from Avid Life Media, the owner of Ashley Madison.

Avid Life is claiming "intellectual property in the data" is being infringed upon and has ordered several sites to be taken down using Digital Millennium Copyright Act (DCMA) requests. Other similar sites, such as HaveIBeenPwned.com, appear to still be operating.

The developers of CheckAshleyMadison confirmed their search site is no longer operational after they were served with a DMCA takedown. They wrote on the website: "During the creation of this site, we made it clear that we wanted to give Ashley Madison's users the ability to check if their accounts have been compromised due to the seemingly faulty and thoughtless work done by Ashley Madison's development team.

"We have given several users who have contacted us information about the leak, and we tried our best to help them understand the situation. In every single case, we have removed information from our server on request by the user.

"Nonetheless, Ashley Madison's legal team has served us with a DMCA takedown request forcing us to shut down this service. We hope that Avid Life Media will follow-up in the coming days with some sort of help to their userbase and a formal apology, rather than try to sweep it under the rug. It truly shows how much the owners of the site care about their users. We also hope that all of you affected by the leak will be able to find some sort of comfort in the near future after the immense effect this will likely have on many of your personal lives."

A statement on AshleyMadisonLeakedData also confirms the site has been removed following a similar takedown. A spokesperson added: "I created this site as I believed that users should have the right to know if their email and data was compromised. Unfortunately I received a takedown notice from Avid Dating Life Media, Inc so I'm forced to shut down this site; sorry for the inconvenience."

There have been arguments that the websites are being removed despite there being no copyright infringement. Andy Sellars, at Harvard Law School's Berkman Center for Internet and Society, told Gizmodo: "Ashley Madison is using the DMCA in a way that it was never designed to be used in order to suppress reporting on the issue. I think it's a rather clean-cut case here. I think there's clearly not infringement in these cases."

Corynne McSherry, legal director for the Electronic Frontier Foundation (EFF), added: "You should only use the DMCA when you're worried about copyright infringement. If it's just people publishing factual information, it's not infringement. It looks to me like some of the stuff that's targeted is just pure facts."

Elsewhere, Joseph Cox, a writer for tech site Motherboard, claimed three of his tweets were removed for copyright infringement after they were alleged to have contained information from within the Madison Avenue leak. Reddit also removed an Ashley Madison Hack subreddit, where some of the data was uploaded, but did not given an official explanation as to why.