Actor(s): Lazarus Group
Recon/Loader malware attributed to Lazarus, disguised as Notepad++ shell extension.
rule win_unidentified_090_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-03-28" version = "1" description = "Detects win.unidentified_090." 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.unidentified_090" malpedia_rule_date = "20230328" malpedia_hash = "9d2d75cef573c1c2d861f5197df8f563b05a305d" malpedia_version = "20230407" 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 = { ff15???????? 85c0 7416 8b4d98 8d458c 50 ff75a0 } // n = 7, score = 100 // ff15???????? | // 85c0 | test eax, eax // 7416 | je 0x18 // 8b4d98 | mov ecx, dword ptr [ebp - 0x68] // 8d458c | lea eax, [ebp - 0x74] // 50 | push eax // ff75a0 | push dword ptr [ebp - 0x60] $sequence_1 = { 2bc6 898d6cf7ffff 89b588f7ffff 3bd0 7747 83bdacf7ffff08 } // n = 6, score = 100 // 2bc6 | sub eax, esi // 898d6cf7ffff | mov dword ptr [ebp - 0x894], ecx // 89b588f7ffff | mov dword ptr [ebp - 0x878], esi // 3bd0 | cmp edx, eax // 7747 | ja 0x49 // 83bdacf7ffff08 | cmp dword ptr [ebp - 0x854], 8 $sequence_2 = { 755f 8bcf 8d5102 668b01 83c102 6685c0 75f5 } // n = 7, score = 100 // 755f | jne 0x61 // 8bcf | mov ecx, edi // 8d5102 | lea edx, [ecx + 2] // 668b01 | mov ax, word ptr [ecx] // 83c102 | add ecx, 2 // 6685c0 | test ax, ax // 75f5 | jne 0xfffffff7 $sequence_3 = { 880a 42 8b0f 83f902 7621 0fb64602 8a8828500210 } // n = 7, score = 100 // 880a | mov byte ptr [edx], cl // 42 | inc edx // 8b0f | mov ecx, dword ptr [edi] // 83f902 | cmp ecx, 2 // 7621 | jbe 0x23 // 0fb64602 | movzx eax, byte ptr [esi + 2] // 8a8828500210 | mov cl, byte ptr [eax + 0x10025028] $sequence_4 = { 8d8d58ffffff e8???????? 83f8ff 0f8483000000 6a00 68???????? 6a0d } // n = 7, score = 100 // 8d8d58ffffff | lea ecx, [ebp - 0xa8] // e8???????? | // 83f8ff | cmp eax, -1 // 0f8483000000 | je 0x89 // 6a00 | push 0 // 68???????? | // 6a0d | push 0xd $sequence_5 = { 57 3bf8 7731 8d0439 83fa10 898550ffffff } // n = 6, score = 100 // 57 | push edi // 3bf8 | cmp edi, eax // 7731 | ja 0x33 // 8d0439 | lea eax, [ecx + edi] // 83fa10 | cmp edx, 0x10 // 898550ffffff | mov dword ptr [ebp - 0xb0], eax $sequence_6 = { 51 50 e8???????? 837de408 8d45d0 ffb518ffffff } // n = 6, score = 100 // 51 | push ecx // 50 | push eax // e8???????? | // 837de408 | cmp dword ptr [ebp - 0x1c], 8 // 8d45d0 | lea eax, [ebp - 0x30] // ffb518ffffff | push dword ptr [ebp - 0xe8] $sequence_7 = { 50 e8???????? 83c40c c78580f7ffff00000000 33c0 c78584f7ffff07000000 8d8db0f7ffff } // n = 7, score = 100 // 50 | push eax // e8???????? | // 83c40c | add esp, 0xc // c78580f7ffff00000000 | mov dword ptr [ebp - 0x880], 0 // 33c0 | xor eax, eax // c78584f7ffff07000000 | mov dword ptr [ebp - 0x87c], 7 // 8d8db0f7ffff | lea ecx, [ebp - 0x850] $sequence_8 = { 33c9 66890c46 8b35???????? 53 ffd6 57 } // n = 6, score = 100 // 33c9 | xor ecx, ecx // 66890c46 | mov word ptr [esi + eax*2], cx // 8b35???????? | // 53 | push ebx // ffd6 | call esi // 57 | push edi $sequence_9 = { 7810 3de4000000 7309 8b04c5c8220210 5d c3 33c0 } // n = 7, score = 100 // 7810 | js 0x12 // 3de4000000 | cmp eax, 0xe4 // 7309 | jae 0xb // 8b04c5c8220210 | mov eax, dword ptr [eax*8 + 0x100222c8] // 5d | pop ebp // c3 | ret // 33c0 | xor eax, eax condition: 7 of them and filesize < 750592 }
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