Developers of CTB-Locker Ransomware Start Using Bitcoin's Blockchain



Ransomware infections have increased dramatically over the last few months and their ingenious authors are now using bitcoin’s blockchain to send file decryption codes to paying victims.

In traditional CTB-Locker ransomware versions, perpetrators have to rely on a network of previously-hacked servers, which host hidden scripts that send decryption keys when victims pay bitcoin ransoms. This solution is very unreliable due to the fact that these hacked servers are frequently patched, and this cuts into the bottom line of the developers.

However, in more recent variants of the ransomware that targets servers, developers have devised a clever way to anonymously deliver decryption keys: embedding them in the OP_RETURN field.

The technique was explained in detail by Denis Sinegubko, a senior malware researcher at internet security firm Sucuri. The OP_RETURN field was implemented in the Bitcoin protocol so that small chunks of data could be added to each transaction.

According to Sinegubko’s post, the new variant of CTB-Locker - which was first observed in March of this year - baits victims into sending a small bitcoin transaction (0.0001 BTC) which decrypts a small portion of the victim’s encrypted files.

He explains in his post:

“If they see 0.0001 BTC, the wallet’s blockchain is appended with a new transaction whose OP_RETURN field contains the decryption key for the two free test files. If the victims pays the full price, they add a transaction with keys for both test and the rest of the encrypted files.”


Despite the “cleverness” of these ransomware developers, Sinegubko’s investigation revealed that very few webmasters pay the ransom, “Out of almost 100 sites I checked, only one had a real “free decryption test” 0.0001 BTC transaction.” he writes.

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Airbnb Acquires Developer Team Behind Bitcoin Tipping Platform ChangeTip



Airbnb has acquired the team behind ChangeCoin, developers of popular bitcoin tipping platform ChangeTip.

According to Quartz, Airbnb has been very interested in blockchain startups and how the novel technology can augment and improve its existing rental business. While Airbnb has acquired the talent behind ChangeTip, the company has little interest in the tipping platform itself.

Figures from the Airbnb Summer Travel report for 2015, show that the company has served almost 17 million renters around the world. With services companies such as Airbnb - where user reputation is of paramount importance - a transparent and immutable user scoring system can be of great benefit.

Airbnb Co-founder Nathan Blecharczyk explained to CityAM recently how user reputation may start to play an even bigger role in the Airbnb ecosystem in the future, “Within the context of Airbnb, your reputation is everything, and I can see it being even more so in the future, whereby you might need a certain reputation in order to have access to certain types of homes,” he said.

A blockchain-based reputation system can make Airbnb digital identities the standard in the burgeoning global sharing economy, and Blecharczyk knows this.

Blecharczyk told CityAM, when asked about blockchain technology:

“But then the question is whether there’s a way to export that and allow access elsewhere to help other sharing economy models really flourish.”


While the ChangeTip platform experienced tremendous user growth over the past two years after receiving $3.5 million in seed capital in December of 2014, ChangeCoin has been unable to find a sustainable business model. According to a party familiar with the Airbnb acquisition, ChangeCoin has been looking for buyers for its intellectual property for the past few months.

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