Stealer is written in Visual Basic.
rule win_darkcloud_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" 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 = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { 83c414 8d4db0 ff15???????? c745fc23000000 8b4d08 894da8 } // n = 6, score = 100 // 83c414 | add esp, 0x14 // 8d4db0 | lea ecx, [ebp - 0x50] // ff15???????? | // c745fc23000000 | mov dword ptr [ebp - 4], 0x23 // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 894da8 | mov dword ptr [ebp - 0x58], ecx $sequence_1 = { 894598 894db0 8945a8 894dc0 8945b8 ff15???????? 50 } // n = 7, score = 100 // 894598 | mov dword ptr [ebp - 0x68], eax // 894db0 | mov dword ptr [ebp - 0x50], ecx // 8945a8 | mov dword ptr [ebp - 0x58], eax // 894dc0 | mov dword ptr [ebp - 0x40], ecx // 8945b8 | mov dword ptr [ebp - 0x48], eax // ff15???????? | // 50 | push eax $sequence_2 = { 6a00 51 8bf0 ff15???????? 50 56 6a00 } // n = 7, score = 100 // 6a00 | push 0 // 51 | push ecx // 8bf0 | mov esi, eax // ff15???????? | // 50 | push eax // 56 | push esi // 6a00 | push 0 $sequence_3 = { 8d8d68ffffff 51 ff15???????? c745fc06000000 ba???????? 8d4dcc ff15???????? } // n = 7, score = 100 // 8d8d68ffffff | lea ecx, [ebp - 0x98] // 51 | push ecx // ff15???????? | // c745fc06000000 | mov dword ptr [ebp - 4], 6 // ba???????? | // 8d4dcc | lea ecx, [ebp - 0x34] // ff15???????? | $sequence_4 = { 8d855cffffff 8d8df8feffff 50 8d954cffffff 51 52 c7851cffffff08000000 } // n = 7, score = 100 // 8d855cffffff | lea eax, [ebp - 0xa4] // 8d8df8feffff | lea ecx, [ebp - 0x108] // 50 | push eax // 8d954cffffff | lea edx, [ebp - 0xb4] // 51 | push ecx // 52 | push edx // c7851cffffff08000000 | mov dword ptr [ebp - 0xe4], 8 $sequence_5 = { 668b55dc 663b954cffffff 0f8ff4000000 c745fc0c000000 8d45dc 894584 c7857cffffff02400000 } // n = 7, score = 100 // 668b55dc | mov dx, word ptr [ebp - 0x24] // 663b954cffffff | cmp dx, word ptr [ebp - 0xb4] // 0f8ff4000000 | jg 0xfa // c745fc0c000000 | mov dword ptr [ebp - 4], 0xc // 8d45dc | lea eax, [ebp - 0x24] // 894584 | mov dword ptr [ebp - 0x7c], eax // c7857cffffff02400000 | mov dword ptr [ebp - 0x84], 0x4002 $sequence_6 = { ff15???????? 8bd0 8d8df0feffff ff15???????? 50 8b559c 52 } // n = 7, score = 100 // ff15???????? | // 8bd0 | mov edx, eax // 8d8df0feffff | lea ecx, [ebp - 0x110] // ff15???????? | // 50 | push eax // 8b559c | mov edx, dword ptr [ebp - 0x64] // 52 | push edx $sequence_7 = { 668b00 8975dc 662d0100 8975cc 0f80e4000000 8975ac 894584 } // n = 7, score = 100 // 668b00 | mov ax, word ptr [eax] // 8975dc | mov dword ptr [ebp - 0x24], esi // 662d0100 | sub ax, 1 // 8975cc | mov dword ptr [ebp - 0x34], esi // 0f80e4000000 | jo 0xea // 8975ac | mov dword ptr [ebp - 0x54], esi // 894584 | mov dword ptr [ebp - 0x7c], eax $sequence_8 = { 50 8d4d94 51 e8???????? 8bd0 8d4d84 ff15???????? } // n = 7, score = 100 // 50 | push eax // 8d4d94 | lea ecx, [ebp - 0x6c] // 51 | push ecx // e8???????? | // 8bd0 | mov edx, eax // 8d4d84 | lea ecx, [ebp - 0x7c] // ff15???????? | $sequence_9 = { ff15???????? 8bd0 8d4da8 ff15???????? 8d5588 52 8d458c } // n = 7, score = 100 // ff15???????? | // 8bd0 | mov edx, eax // 8d4da8 | lea ecx, [ebp - 0x58] // ff15???????? | // 8d5588 | lea edx, [ebp - 0x78] // 52 | push edx // 8d458c | lea eax, [ebp - 0x74] condition: 7 of them and filesize < 622592 }
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