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 = "2023-01-25" 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 = "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 = { 0f8487020000 660f1f840000000000 688c090000 8d8504f0ffff 6a00 50 e8???????? } // n = 7, score = 100 // 0f8487020000 | je 0x28d // 660f1f840000000000 | nop word ptr [eax + eax] // 688c090000 | push 0x98c // 8d8504f0ffff | lea eax, [ebp - 0xffc] // 6a00 | push 0 // 50 | push eax // e8???????? | $sequence_1 = { 8bb568f7ffff eb21 52 51 c68534f7ffff00 8d8d98f7ffff } // n = 6, score = 100 // 8bb568f7ffff | mov esi, dword ptr [ebp - 0x898] // eb21 | jmp 0x23 // 52 | push edx // 51 | push ecx // c68534f7ffff00 | mov byte ptr [ebp - 0x8cc], 0 // 8d8d98f7ffff | lea ecx, [ebp - 0x868] $sequence_2 = { 48 f7d8 1bc0 40 a3???????? e9???????? 68???????? } // n = 7, score = 100 // 48 | dec eax // f7d8 | neg eax // 1bc0 | sbb eax, eax // 40 | inc eax // a3???????? | // e9???????? | // 68???????? | $sequence_3 = { e9???????? 8b7df4 8b45f0 8b4df8 8b048540a20210 f644082840 7405 } // n = 7, score = 100 // e9???????? | // 8b7df4 | mov edi, dword ptr [ebp - 0xc] // 8b45f0 | mov eax, dword ptr [ebp - 0x10] // 8b4df8 | mov ecx, dword ptr [ebp - 8] // 8b048540a20210 | mov eax, dword ptr [eax*4 + 0x1002a240] // f644082840 | test byte ptr [eax + ecx + 0x28], 0x40 // 7405 | je 7 $sequence_4 = { 7625 8b45f0 8d0470 3d???????? 7218 81fa???????? } // n = 6, score = 100 // 7625 | jbe 0x27 // 8b45f0 | mov eax, dword ptr [ebp - 0x10] // 8d0470 | lea eax, [eax + esi*2] // 3d???????? | // 7218 | jb 0x1a // 81fa???????? | $sequence_5 = { 8d0412 50 ffb568f7ffff 51 e8???????? 83c40c 33c0 } // n = 7, score = 100 // 8d0412 | lea eax, [edx + edx] // 50 | push eax // ffb568f7ffff | push dword ptr [ebp - 0x898] // 51 | push ecx // e8???????? | // 83c40c | add esp, 0xc // 33c0 | xor eax, eax $sequence_6 = { 83c702 3b7d88 75bc c645fc04 8d4dbc } // n = 5, score = 100 // 83c702 | add edi, 2 // 3b7d88 | cmp edi, dword ptr [ebp - 0x78] // 75bc | jne 0xffffffbe // c645fc04 | mov byte ptr [ebp - 4], 4 // 8d4dbc | lea ecx, [ebp - 0x44] $sequence_7 = { 50 ffd7 5f c70600000000 c7460400000000 c7460800000000 } // n = 6, score = 100 // 50 | push eax // ffd7 | call edi // 5f | pop edi // c70600000000 | mov dword ptr [esi], 0 // c7460400000000 | mov dword ptr [esi + 4], 0 // c7460800000000 | mov dword ptr [esi + 8], 0 $sequence_8 = { 8b4628 85c0 740a 50 ffd7 c7462800000000 8b4620 } // n = 7, score = 100 // 8b4628 | mov eax, dword ptr [esi + 0x28] // 85c0 | test eax, eax // 740a | je 0xc // 50 | push eax // ffd7 | call edi // c7462800000000 | mov dword ptr [esi + 0x28], 0 // 8b4620 | mov eax, dword ptr [esi + 0x20] $sequence_9 = { 57 e8???????? 8b9568ffffff 8bc2 8b8d64ffffff } // n = 5, score = 100 // 57 | push edi // e8???????? | // 8b9568ffffff | mov edx, dword ptr [ebp - 0x98] // 8bc2 | mov eax, edx // 8b8d64ffffff | mov ecx, dword ptr [ebp - 0x9c] condition: 7 of them and filesize < 750592 }
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