unpack ( endian + "2L", block ) ( v6, v7, v8, v9 ) = struct. Variant TEA code converted to python: #Modified from ĭef ul ( val ): return val & 0xffffffff def test_tea ( key, block, n = 32, endian = "!" ): v2, v3 = struct. This secondary layer I haven’t seen used in any of the other malware so it was either a wrapper layer designed to be able to be added to Emotet or a wrapper layer option in the crypter or a secondary crypter all together being used for Anti check purposes. For other malware using this crypter recently was Emotet, which was using a secondary loader full of Anti checks. This particular crypter ultimately ends up decoding an unpacked PE file sitting on code to load it using a variant of TEA. Doing this is an easy way to defeat heuristics designed to find code reuse and makes writing YARA rules sometimes challenging, but it also makes the crypter more interesting because these types of crypters if kept private are usually used for very long period of times. Lots of obfuscation has gone into this crypter over time and judging my tracking it uses a dynamic stub generator which basically takes small sections of code and either turns them into useless functions or adds in useless Windows API functions calls or even useless opcodes between the instructions. The sample talking about in the article by is what really caught my attention, because it was using a crypter I had been following for some time and made mentioned of briefly in a blog post I did at work. ![]() ![]() It only takes one big crimeware actor however to start pushing ransomware to gently remind us that ransomware is by no means dead.Ī number of articles have covered the various portions of GandCrab, including how to unpack it. ![]() After a 2017 year of dime a dozen ransomware variants, 2018 seems to be a year of dime a dozen crypto miners.
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