Malware written in Nim, stealing data including discord tokens from browsers, exfiltrating the results via a Discord webhook.
rule win_nimgrabber_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.nimgrabber." 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.nimgrabber" 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 = { 8d44240c 8944240c 8b54240c 31c0 85d2 740c 8b442414 } // n = 7, score = 200 // 8d44240c | lea eax, [esp + 0xc] // 8944240c | mov dword ptr [esp + 0xc], eax // 8b54240c | mov edx, dword ptr [esp + 0xc] // 31c0 | xor eax, eax // 85d2 | test edx, edx // 740c | je 0xe // 8b442414 | mov eax, dword ptr [esp + 0x14] $sequence_1 = { 3b5f44 0f823b140000 3b5f48 0f8247140000 3b5f4c 0f8279140000 3b5f50 } // n = 7, score = 200 // 3b5f44 | cmp ebx, dword ptr [edi + 0x44] // 0f823b140000 | jb 0x1441 // 3b5f48 | cmp ebx, dword ptr [edi + 0x48] // 0f8247140000 | jb 0x144d // 3b5f4c | cmp ebx, dword ptr [edi + 0x4c] // 0f8279140000 | jb 0x147f // 3b5f50 | cmp ebx, dword ptr [edi + 0x50] $sequence_2 = { b9???????? 8d50f8 e8???????? 897b14 8b530c 8b4314 } // n = 6, score = 200 // b9???????? | // 8d50f8 | lea edx, [eax - 8] // e8???????? | // 897b14 | mov dword ptr [ebx + 0x14], edi // 8b530c | mov edx, dword ptr [ebx + 0xc] // 8b4314 | mov eax, dword ptr [ebx + 0x14] $sequence_3 = { eb03 83ea01 890424 89542404 e8???????? 8b442468 8b4c245c } // n = 7, score = 200 // eb03 | jmp 5 // 83ea01 | sub edx, 1 // 890424 | mov dword ptr [esp], eax // 89542404 | mov dword ptr [esp + 4], edx // e8???????? | // 8b442468 | mov eax, dword ptr [esp + 0x68] // 8b4c245c | mov ecx, dword ptr [esp + 0x5c] $sequence_4 = { 03b37c100000 83ec08 8b442418 89b37c100000 83c008 c7470401000000 83c42c } // n = 7, score = 200 // 03b37c100000 | add esi, dword ptr [ebx + 0x107c] // 83ec08 | sub esp, 8 // 8b442418 | mov eax, dword ptr [esp + 0x18] // 89b37c100000 | mov dword ptr [ebx + 0x107c], esi // 83c008 | add eax, 8 // c7470401000000 | mov dword ptr [edi + 4], 1 // 83c42c | add esp, 0x2c $sequence_5 = { 8b6c2460 85c0 0f84a7000000 8b10 85d2 0f849d000000 8d44243c } // n = 7, score = 200 // 8b6c2460 | mov ebp, dword ptr [esp + 0x60] // 85c0 | test eax, eax // 0f84a7000000 | je 0xad // 8b10 | mov edx, dword ptr [eax] // 85d2 | test edx, edx // 0f849d000000 | je 0xa3 // 8d44243c | lea eax, [esp + 0x3c] $sequence_6 = { 83ec0c 85c0 0f855dfdffff c70424???????? e8???????? c7042401000000 e8???????? } // n = 7, score = 200 // 83ec0c | sub esp, 0xc // 85c0 | test eax, eax // 0f855dfdffff | jne 0xfffffd63 // c70424???????? | // e8???????? | // c7042401000000 | mov dword ptr [esp], 1 // e8???????? | $sequence_7 = { 83c050 89442478 8b8424f8000000 8b4810 8b5814 85c9 0f84f0060000 } // n = 7, score = 200 // 83c050 | add eax, 0x50 // 89442478 | mov dword ptr [esp + 0x78], eax // 8b8424f8000000 | mov eax, dword ptr [esp + 0xf8] // 8b4810 | mov ecx, dword ptr [eax + 0x10] // 8b5814 | mov ebx, dword ptr [eax + 0x14] // 85c9 | test ecx, ecx // 0f84f0060000 | je 0x6f6 $sequence_8 = { 57 56 53 89cb 83ec20 c744240400000000 8d54241f } // n = 7, score = 200 // 57 | push edi // 56 | push esi // 53 | push ebx // 89cb | mov ebx, ecx // 83ec20 | sub esp, 0x20 // c744240400000000 | mov dword ptr [esp + 4], 0 // 8d54241f | lea edx, [esp + 0x1f] $sequence_9 = { be0e000000 e9???????? c744241001000000 c1eb0f bf01000000 e9???????? c744241002000000 } // n = 7, score = 200 // be0e000000 | mov esi, 0xe // e9???????? | // c744241001000000 | mov dword ptr [esp + 0x10], 1 // c1eb0f | shr ebx, 0xf // bf01000000 | mov edi, 1 // e9???????? | // c744241002000000 | mov dword ptr [esp + 0x10], 2 condition: 7 of them and filesize < 1238016 }
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