Stealer is written in Visual Basic.
rule win_darkcloud_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.darkcloud." 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.darkcloud" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { 8b45b8 8b8df8feffff 3b4810 730c c785c0fdffff00000000 eb0c ff15???????? } // n = 7, score = 100 // 8b45b8 | mov eax, dword ptr [ebp - 0x48] // 8b8df8feffff | mov ecx, dword ptr [ebp - 0x108] // 3b4810 | cmp ecx, dword ptr [eax + 0x10] // 730c | jae 0xe // c785c0fdffff00000000 | mov dword ptr [ebp - 0x240], 0 // eb0c | jmp 0xe // ff15???????? | $sequence_1 = { 8b55dc 66833a01 7547 0fbf45d0 8b4ddc 2b4114 8985f8feffff } // n = 7, score = 100 // 8b55dc | mov edx, dword ptr [ebp - 0x24] // 66833a01 | cmp word ptr [edx], 1 // 7547 | jne 0x49 // 0fbf45d0 | movsx eax, word ptr [ebp - 0x30] // 8b4ddc | mov ecx, dword ptr [ebp - 0x24] // 2b4114 | sub eax, dword ptr [ecx + 0x14] // 8985f8feffff | mov dword ptr [ebp - 0x108], eax $sequence_2 = { 0fbf8d44ffffff 85c9 7414 c745fc34000000 8b15???????? 52 ff15???????? } // n = 7, score = 100 // 0fbf8d44ffffff | movsx ecx, word ptr [ebp - 0xbc] // 85c9 | test ecx, ecx // 7414 | je 0x16 // c745fc34000000 | mov dword ptr [ebp - 4], 0x34 // 8b15???????? | // 52 | push edx // ff15???????? | $sequence_3 = { 730c c7857cfcffff00000000 eb0c ff15???????? 89857cfcffff 8b8dd8fdffff 6bc90c } // n = 7, score = 100 // 730c | jae 0xe // c7857cfcffff00000000 | mov dword ptr [ebp - 0x384], 0 // eb0c | jmp 0xe // ff15???????? | // 89857cfcffff | mov dword ptr [ebp - 0x384], eax // 8b8dd8fdffff | mov ecx, dword ptr [ebp - 0x228] // 6bc90c | imul ecx, ecx, 0xc $sequence_4 = { 51 52 e8???????? 8bf0 ffd7 3bf3 0f8cbe020000 } // n = 7, score = 100 // 51 | push ecx // 52 | push edx // e8???????? | // 8bf0 | mov esi, eax // ffd7 | call edi // 3bf3 | cmp esi, ebx // 0f8cbe020000 | jl 0x2c4 $sequence_5 = { 68???????? 8b9584feffff 52 8b8580feffff 50 ff15???????? 898520fdffff } // n = 7, score = 100 // 68???????? | // 8b9584feffff | mov edx, dword ptr [ebp - 0x17c] // 52 | push edx // 8b8580feffff | mov eax, dword ptr [ebp - 0x180] // 50 | push eax // ff15???????? | // 898520fdffff | mov dword ptr [ebp - 0x2e0], eax $sequence_6 = { 8d4d94 ffd3 8b45e4 6a00 50 e8???????? 8d8d7cffffff } // n = 7, score = 100 // 8d4d94 | lea ecx, [ebp - 0x6c] // ffd3 | call ebx // 8b45e4 | mov eax, dword ptr [ebp - 0x1c] // 6a00 | push 0 // 50 | push eax // e8???????? | // 8d8d7cffffff | lea ecx, [ebp - 0x84] $sequence_7 = { ffd6 8b4de4 50 51 ff9394000000 85c0 } // n = 6, score = 100 // ffd6 | call esi // 8b4de4 | mov ecx, dword ptr [ebp - 0x1c] // 50 | push eax // 51 | push ecx // ff9394000000 | call dword ptr [ebx + 0x94] // 85c0 | test eax, eax $sequence_8 = { ff15???????? ba???????? 8d4dcc ff15???????? 8b55c8 89951cffffff c745c800000000 } // n = 7, score = 100 // ff15???????? | // ba???????? | // 8d4dcc | lea ecx, [ebp - 0x34] // ff15???????? | // 8b55c8 | mov edx, dword ptr [ebp - 0x38] // 89951cffffff | mov dword ptr [ebp - 0xe4], edx // c745c800000000 | mov dword ptr [ebp - 0x38], 0 $sequence_9 = { c745fc18000000 ba???????? 8d4d98 ff15???????? 8d5598 52 e8???????? } // n = 7, score = 100 // c745fc18000000 | mov dword ptr [ebp - 4], 0x18 // ba???????? | // 8d4d98 | lea ecx, [ebp - 0x68] // ff15???????? | // 8d5598 | lea edx, [ebp - 0x68] // 52 | push edx // e8???????? | condition: 7 of them and filesize < 622592 }
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