Website Ransomware Not Viable – Yet

Wednesday, April 20, 2016 @ 12:04 PM gHale

There is a new method attackers are using in their efforts to toughen up ransomware for websites.

A variant of the CTB-Locker ransomware came to light that targets encrypting websites, but Denis Sinegubko, founder of Unmask Parasites and a senior malware researcher at Sucuri said in a blog post that method has not been a success, yet.

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As it turns out, the researchers said no website owner affected by the ransomware paid the ransom.

Unlike CTB-Locker for desktop computers, CTB-Locker for Websites focused on compromising servers and encrypting the files that normally keep websites online. Most website owners affected by this malware were able to restore their files from backups, while those who haven’t yet might have actually abandoned their websites.

What CTB-Locker for Websites does do is it uses blockchains, which are chains of verified transactions used in the Bitcoin world, to transmit decryption keys. Since blockchains are public, they can end up tracked by anyone, and specialized services exist that allow users view Bitcoin blockchains.

CTB-Locker operators are taking advantage of a feature introduced in 2014, when the Bitcoin protocol started allowing for small blocks of arbitrary text (metadata) to be in the OP_RETURN field. The feature made blockchains applicable to fields unrelated to Bitcoin, and attackers are trying to take advantage of it.

The ransomware operators create a new Bitcoin wallet with a unique address for each encrypted website, and they publish the address to the ransom demand page, Sucuri researchers said. When the victim pays the ransom, the hackers check the transferred sum and the wallet’s blockchain ends up appended with a new transaction whose OP_RETURN field contains the decryption key.

The OP_RETURN transaction ends up validated and propagated through distributed nodes of the Bitcoin system, and it also becomes visible in services that provide information on blockchains. This is why attackers advise victims to track their transactions on the site.

The use of blockchain to transmit decryption keys is much more reliable than using payment gates and third-party hacked sites, the researchers said. They also said the March version of the CTB-Locker reads the keys directly from public, more reliable blockchain information services, making the entire process public and transparent, while also keeping things anonymous and not traceable to real IPs.

“Even smart use of a new technology is not a guarantee of success when you port a tried-and-true business model from one niche to another,” Sinegubko said. “The devil is in the details. In the case of website crypto-ransomware, such overlooked details supply easy access to backups for most websites, which allows them to ignore ransom demands.

“Nonetheless, I’m sure we’ll see more new waves of website ransomware attacks as hackers try to change their tactics and search for a magic recipe that will allow them to get money directly from owners of compromised websites.”

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