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Friday, 24 November 2017 08:54

Necurs botnet spreading new strain of Windows ransomware Featured

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The Internet's biggest spam botnet Necurs has been spreading a strain of Windows ransomware known as Scarab over the last two days, security companies say.

Necurs has something in the range of five to six million infected hosts online monthly, according to F-Secure. Its service model has the entire infection chain, from spam emails with malicious malware downloader attachments, to hosting payloads on compromised websites.

scarab

The emails arrive with subject lines like "Scanned from (Lexmark/HP/Canon/Epson)”. The attachment is named as “image2017-11-23-(7 random digits).7z“ and contains a VBScript downloader that pulls down the Scarab ransomware.

Security firm Forcepoint said it had noticed about 12.5 million emails of this kind in six hours beginning at 7.30GMT on Thursday.

"Based on our telemetry, the majority of the traffic is being sent to the .com top-level domain. However, this was followed by region-specific TLDs for the United Kingdom, Australia, France and Germany," the company said.

F-Secure said the Scarab ransomware was relatively new and was observed last June, with its code being based on the open source “ransomware proof-of-concept” called HiddenTear.

The latest version has no change in filenames, but appends a new file extension to the encrypted files with “.[suupport@protonmail.com].scarab”.

The ransom note reads:

ransomnote

Forcepoint said that as with previous Necurs campaigns, the VBScript contained a number of references to Game of Thrones.

It said that the Scarab ransomware that was dropped had the file name sevnz.exe.

"Once installed it proceeds to encrypt files, adding the extension “.[suupport@protonmail.com].scarab” to affected files. A ransom note with the filename “IF YOU WANT TO GET ALL YOUR FILES BACK, PLEASE READ THIS.TXT” is dropped within each affected directory," the company said.

"The misspelling of 'support' is present in both the modified filenames and the ransom note, and is presumably a result of the availability of email addresses on the Protonmail service.

"Unusually, the note does not specify the amount being demanded, instead simply stating that "the price depends on how fast you write to us". This note is also automatically opened by the malware after execution."

Graphic: courtesy Forcepoint. Screenshot: courtesy F-Secure


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Sam Varghese

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Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

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