A new strain of Teslacrypt implements sophisticated evasion

Pierluigi Paganini April 21, 2016

The authors of the TeslaCrypt ransomware have improved it by implementing new sophisticated evasion techniques and targeting new file types.

The authors of the TeslaCrypt ransomware have introduced a couple of significant improvements, the new variant Version 4.1 has been in circulation for about a week. According to the experts at Endgame Inc., VXers have invested heavily in obfuscation and evasion techniques, and the malicious code can also encrypt new file extensions (.7z; .apk; .asset; .avi; .bak; .bik; .bsa; .csv; .d3dbsp; .das; .forge; .iwi; .lbf; .litemod; .litesql; .ltx; .m4a; .mp4; .rar; .re4; .sav; .slm; .sql; .tiff; .upk; .wma; .wmv; and .wallet).

“As our latest research on TeslaCrypt demonstrates, ransomware not only is becoming more widespread, but it is also becoming more sophisticated and adaptable. TeslaCrypt 4.1A  is only a week old and contains an even greater variety of stealth and obfuscation techniques than its previous variants, the earliest of which is just over a year old.” states a report published by Endgame Inc.

The ransomware also targets backup files by deleting the Volume Shadow Copy, the new strain uses AES 256 for file encryption.

Like its predecessors, this new strain of Teslacrypt is spread as attachments of spam campaigns purporting to be shipping delivery notifications.

When the victims open the malicious .zip file sent as the attachment, a JavaScript downloader using Wscript is executed in order to download the TeslaCrypt ransomware from greetingsyoungqq[.]com/80.exe.

The Teslacrypt 4.1A ransomware also uses COM objects and deletes zone identifiers to evade the detection.

Teslacrypt ransomware 4 1 A

The ransomware also implements an anti-monitoring feature that terminates several Windows processes, including the Task Manager; Registry Editor; Command Shell, SysInternals Process Explorer and System Configuration.

This variant of TeslaCrypt maintains the persistence by making a copy of itself to the disk and creating a registry entry that points to the copy.

The ransomware attacks are the headlines in this first part of the year, and the situation is worsening.

“Only four months into 2016, as our timeline demonstrates, this may very well be the year of the ransomware attack. These kinds of opportunistic attacks can be very lucrative and sophisticated, and should increasingly be on the radar of both high-value organizations as well as individuals. ” close the post

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Pierluigi Paganini

(Security Affairs – cybercrime, Ransomware)

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