Mandiant associates this with UNC4191, this malware spreads to removable drives.
rule win_darkdew_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.darkdew." info = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.6.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.darkdew" malpedia_rule_date = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" malpedia_license = "CC BY-SA 4.0" malpedia_sharing = "TLP:WHITE" /* DISCLAIMER * The strings used in this rule have been automatically selected from the * disassembly of memory dumps and unpacked files, using YARA-Signator. * The code and documentation is published here: * https://github.com/fxb-cocacoding/yara-signator * As Malpedia is used as data source, please note that for a given * number of families, only single samples are documented. * This likely impacts the degree of generalization these rules will offer. * Take the described generation method also into consideration when you * apply the rules in your use cases and assign them confidence levels. */ strings: $sequence_0 = { 5d c3 e8???????? 68???????? ffd6 e8???????? e8???????? } // n = 7, score = 100 // 5d | pop ebp // c3 | ret // e8???????? | // 68???????? | // ffd6 | call esi // e8???????? | // e8???????? | $sequence_1 = { 8bd0 c645fc01 837a1408 7202 } // n = 4, score = 100 // 8bd0 | mov edx, eax // c645fc01 | mov byte ptr [ebp - 4], 1 // 837a1408 | cmp dword ptr [edx + 0x14], 8 // 7202 | jb 4 $sequence_2 = { d1f8 894dfc 8955f4 8945f0 56 57 3bd0 } // n = 7, score = 100 // d1f8 | sar eax, 1 // 894dfc | mov dword ptr [ebp - 4], ecx // 8955f4 | mov dword ptr [ebp - 0xc], edx // 8945f0 | mov dword ptr [ebp - 0x10], eax // 56 | push esi // 57 | push edi // 3bd0 | cmp edx, eax $sequence_3 = { 0f87a8040000 52 51 e8???????? 83c408 c645fc17 8b55cc } // n = 7, score = 100 // 0f87a8040000 | ja 0x4ae // 52 | push edx // 51 | push ecx // e8???????? | // 83c408 | add esp, 8 // c645fc17 | mov byte ptr [ebp - 4], 0x17 // 8b55cc | mov edx, dword ptr [ebp - 0x34] $sequence_4 = { c78554feffff00000000 c7856efeffff00000000 898d60feffff c78558feffff02000000 ff15???????? c645fc11 } // n = 6, score = 100 // c78554feffff00000000 | mov dword ptr [ebp - 0x1ac], 0 // c7856efeffff00000000 | mov dword ptr [ebp - 0x192], 0 // 898d60feffff | mov dword ptr [ebp - 0x1a0], ecx // c78558feffff02000000 | mov dword ptr [ebp - 0x1a8], 2 // ff15???????? | // c645fc11 | mov byte ptr [ebp - 4], 0x11 $sequence_5 = { eb1a c685e8feffff00 8d8d68ffffff ffb5e8feffff } // n = 4, score = 100 // eb1a | jmp 0x1c // c685e8feffff00 | mov byte ptr [ebp - 0x118], 0 // 8d8d68ffffff | lea ecx, [ebp - 0x98] // ffb5e8feffff | push dword ptr [ebp - 0x118] $sequence_6 = { b991000000 894508 8dbda8fdffff 8bf0 8d8574fcffff 50 } // n = 6, score = 100 // b991000000 | mov ecx, 0x91 // 894508 | mov dword ptr [ebp + 8], eax // 8dbda8fdffff | lea edi, [ebp - 0x258] // 8bf0 | mov esi, eax // 8d8574fcffff | lea eax, [ebp - 0x38c] // 50 | push eax $sequence_7 = { 83e03f c1f906 6bf038 03348da0f30110 } // n = 4, score = 100 // 83e03f | and eax, 0x3f // c1f906 | sar ecx, 6 // 6bf038 | imul esi, eax, 0x38 // 03348da0f30110 | add esi, dword ptr [ecx*4 + 0x1001f3a0] $sequence_8 = { 8a01 8d4901 88440aff 84c0 75f3 b950000000 8db578feffff } // n = 7, score = 100 // 8a01 | mov al, byte ptr [ecx] // 8d4901 | lea ecx, [ecx + 1] // 88440aff | mov byte ptr [edx + ecx - 1], al // 84c0 | test al, al // 75f3 | jne 0xfffffff5 // b950000000 | mov ecx, 0x50 // 8db578feffff | lea esi, [ebp - 0x188] $sequence_9 = { 50 68???????? ffd3 837dcc10 8d45b8 8b35???????? 0f4345b8 } // n = 7, score = 100 // 50 | push eax // 68???????? | // ffd3 | call ebx // 837dcc10 | cmp dword ptr [ebp - 0x34], 0x10 // 8d45b8 | lea eax, [ebp - 0x48] // 8b35???????? | // 0f4345b8 | cmovae eax, dword ptr [ebp - 0x48] condition: 7 of them and filesize < 279552 }
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