ESET assess the differences between CryptoFortress and TorrentLocker: two very different strains of ransomware.
Last week, Kafeine published a blog post about a ransomware being distributed by the Nuclear Pack exploit kit. This ransomware identify itself as “CryptoFortress”, but the ransom message and payment page both looks like an already known ransomware: TorrentLocker.
After further analysis, ESET researchers found out is the two threats are in fact very different. It appears the group behind CryptoFortress has stolen the HTML templates with its CSS. The malware code and the scheme are actually very different. Here is a table summering the similarities and differences:
|File encryption||AES-256 CBC||AES-256 ECB|
|Hardcoded C&C server||Yes||No|
|Ransom page location||Fetched from C&C server||Included in malware|
|Payment page location||Onion-routed (but same server as the hardcoded C&C)||Onion-routed|
|AES key encryption||RSA-1024||RSA-1024|
|Cryptographic library||LibTomCrypt||Microsoft CryptoAPI|
|Encrypted portion of files||2 Mb at beginning of file||First 50% of the file, up to 5 Mb|
|Payment||Bitcoin (variable amount)||1.0 Bitcoin|
Last Friday, Renaud Tabary from Lexsi published a complete analysis of the new ransomware. ESET researchers have independently analyzed the CryptoFortress samples before Lexsi released the details. The technical details described in the article matches our findings.
ESET Telemetry also shows TorrentLocker campaign is still propagating via spam messages. Both campaign are now running in parallel.
CryptoFortress: Teerac.A (aka TorrentLocker) got a new identity, http://malware.dontneedcoffee.com/2015/03/cryptofortress-teeraca-aka.html
|SHA-1 sum||ESET Detection name|
CryptoFortress public key
-----BEGIN PUBLIC KEY-----
-----END PUBLIC KEY-----