Extortionists becoming more helpful as new ransomware generation bows

Ransomware authors are increasingly focusing on customer service in an attempt to improve the efficacy of attacks, security analysts have warned as a new version of CryptoWall malware appeared and Australian researchers warned that carefully-crafted localised ransomware is increasingly hitting its mark.

An analysis of Australianised attacks by the TorrentLocker malware, conducted through a joint research effort between Deakin University researchers Christopher Ke and Yang Xiang along with security analysts from Trend Micro, found that ransomware specialists had gone to great lengths to cover their tracks.

These steps included regular URL redirection, with redirect rules frequently taken down after short periods and even the structure of target URLs changing on a regular basis. The malware also establishes a regularly-changing hierarchy of server IP addresses, with short time to live (TTL) settings ensuring that DNS changes would quickly propagate – obscuring efforts to trace the malware's line of command.

Spam emails provided the infection vector, with “carefully crafted” spam copying details from Australia Post parcel tracking emails and NSW Office of State Revenue penalty notices. Landing pages were similarly carefully created, with fake WhoIS information used and clear efforts to avoid relationships between landing page domains and IP addresses.

“The number of Web servers hosting landing pages was relatively small and the attacker used more sophisticated mechanisms to hide server locations,” the analysts observed. “In conjunction with the short DNS TTL, the domains could perform fast fluxing to avoid being tracked.”

The Deakin-Trend Micro audit found some 55 domains emulating Australia Post sites while 29 domains were emulating OSR sites. These sites would facilitate access to a hosted payload stored on a third-party Web storage service, with command-and-control servers hosted in Russia.

Once a victim's files have been encrypted, the researchers noted that the user interface has been designed to be “very helpful in providing information about how to pay using Bitcoins”.

This observation correlates with a growing trend towards user friendliness amongst ransomware providers, who are tweaking their infection vectors but continuing to look for ways to simplify the purchase of Bitcoin required as payment to unlock infected systems.

While it has tightened up its performance and improved detection of virtual environments designed to catch it in action, the new CryptoWall 3.0 ransomware has, security analysis firm KnowBe4 observes, also improved guidance of customers by extending the payment deadline from 5 days to a full week. Ransom note file names have, the site notes, “have been made easier to read with detailed information on how to access the ransom payment site.”

The result is an anomaly as ransomware authors become at once nastier and more helpful to their victims.

“Ironically, as cyber criminals get more sophisticated, so do their efforts to improve their extortion methods,” KnowBe4 CEO Stu Sjouwerman said in a statement.

“While a hard working criminal is an oxymoron, CryptoWall 3.0 shows they are working diligently to make the ransom payment and decryption process easier.”

Australians are likely to be particularly susceptible to the new ransomware: the previous CryptoWall is said to have already infected over 700,000 victims, while Microsoft reports surging encounter numbers and December reports found that more than 9400 computers in Australia had been infected with TorrentLocker – putting Australia second only to Turkey in the number of infections worldwide.

An earlier Trend Micro analysis of ransomware similarly found Australians to be more susceptible to ransomware than residents of other countries.

This article is brought to you by Enex TestLab, content directors for CSO Australia.

This article is brought to you by Enex TestLab, content directors for CSO Australia.

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Tags Enex TestLabKnowBe4CSO AustraliaTorrentLockerDeakin-Trend MicroDNS TTLCryptoWall malwareYang Xiang

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