rule win_privateloader_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-09-17" version = "1" description = "Detects win.privateloader." 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.privateloader" malpedia_rule_date = "20260916" malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6" malpedia_version = "20260917" 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 = { 55 8bec 83ec28 894dd8 8b4508 8945e4 8b4de4 } // n = 7, score = 600 // 55 | push ebp // 8bec | mov ebp, esp // 83ec28 | sub esp, 0x28 // 894dd8 | mov dword ptr [ebp - 0x28], ecx // 8b4508 | mov eax, dword ptr [ebp + 8] // 8945e4 | mov dword ptr [ebp - 0x1c], eax // 8b4de4 | mov ecx, dword ptr [ebp - 0x1c] $sequence_1 = { 8b4d10 51 8b55e8 03550c 52 8b4dd8 e8???????? } // n = 7, score = 600 // 8b4d10 | mov ecx, dword ptr [ebp + 0x10] // 51 | push ecx // 8b55e8 | mov edx, dword ptr [ebp - 0x18] // 03550c | add edx, dword ptr [ebp + 0xc] // 52 | push edx // 8b4dd8 | mov ecx, dword ptr [ebp - 0x28] // e8???????? | $sequence_2 = { 83ec1c 894df8 8b45f8 8b4810 894df4 } // n = 5, score = 600 // 83ec1c | sub esp, 0x1c // 894df8 | mov dword ptr [ebp - 8], ecx // 8b45f8 | mov eax, dword ptr [ebp - 8] // 8b4810 | mov ecx, dword ptr [eax + 0x10] // 894df4 | mov dword ptr [ebp - 0xc], ecx $sequence_3 = { 8b45d8 8b4ddc 8b55d0 8b75d4 } // n = 4, score = 600 // 8b45d8 | mov eax, dword ptr [ebp - 0x28] // 8b4ddc | mov ecx, dword ptr [ebp - 0x24] // 8b55d0 | mov edx, dword ptr [ebp - 0x30] // 8b75d4 | mov esi, dword ptr [ebp - 0x2c] $sequence_4 = { 8945fc 8b4dfc 894df4 8b55fc 837a1408 7209 } // n = 6, score = 600 // 8945fc | mov dword ptr [ebp - 4], eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 894df4 | mov dword ptr [ebp - 0xc], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // 837a1408 | cmp dword ptr [edx + 0x14], 8 // 7209 | jb 0xb $sequence_5 = { 8b02 894510 8b4d08 894dfc 8b55fc 8955e8 8b45fc } // n = 7, score = 600 // 8b02 | mov eax, dword ptr [edx] // 894510 | mov dword ptr [ebp + 0x10], eax // 8b4d08 | mov ecx, dword ptr [ebp + 8] // 894dfc | mov dword ptr [ebp - 4], ecx // 8b55fc | mov edx, dword ptr [ebp - 4] // 8955e8 | mov dword ptr [ebp - 0x18], edx // 8b45fc | mov eax, dword ptr [ebp - 4] $sequence_6 = { 8b0d???????? 83f100 6a00 6a00 51 } // n = 5, score = 600 // 8b0d???????? | // 83f100 | xor ecx, 0 // 6a00 | push 0 // 6a00 | push 0 // 51 | push ecx $sequence_7 = { 8b4214 2b45f4 394508 7777 8b4df4 } // n = 5, score = 600 // 8b4214 | mov eax, dword ptr [edx + 0x14] // 2b45f4 | sub eax, dword ptr [ebp - 0xc] // 394508 | cmp dword ptr [ebp + 8], eax // 7777 | ja 0x79 // 8b4df4 | mov ecx, dword ptr [ebp - 0xc] $sequence_8 = { e8???????? 33d2 b93f000000 f7f1 } // n = 4, score = 500 // e8???????? | // 33d2 | xor edx, edx // b93f000000 | mov ecx, 0x3f // f7f1 | div ecx $sequence_9 = { 8bec 81ec68010000 a1???????? 33c5 8945fc 56 57 } // n = 7, score = 400 // 8bec | mov ebp, esp // 81ec68010000 | sub esp, 0x168 // a1???????? | // 33c5 | xor eax, ebp // 8945fc | mov dword ptr [ebp - 4], eax // 56 | push esi // 57 | push edi $sequence_10 = { 56 ff15???????? a3???????? 33c0 5e c3 3b0d???????? } // n = 7, score = 400 // 56 | push esi // ff15???????? | // a3???????? | // 33c0 | xor eax, eax // 5e | pop esi // c3 | ret // 3b0d???????? | $sequence_11 = { e8???????? 6bc007 33c9 41 6bc903 } // n = 5, score = 400 // e8???????? | // 6bc007 | imul eax, eax, 7 // 33c9 | xor ecx, ecx // 41 | inc ecx // 6bc903 | imul ecx, ecx, 3 $sequence_12 = { e8???????? 83c610 83c002 83ef08 a907000000 0f853effffff } // n = 6, score = 400 // e8???????? | // 83c610 | add esi, 0x10 // 83c002 | add eax, 2 // 83ef08 | sub edi, 8 // a907000000 | test eax, 7 // 0f853effffff | jne 0xffffff44 $sequence_13 = { 8b4590 8b4d94 8b5588 8b758c } // n = 4, score = 400 // 8b4590 | mov eax, dword ptr [ebp - 0x70] // 8b4d94 | mov ecx, dword ptr [ebp - 0x6c] // 8b5588 | mov edx, dword ptr [ebp - 0x78] // 8b758c | mov esi, dword ptr [ebp - 0x74] $sequence_14 = { 0bc8 56 57 7529 } // n = 4, score = 300 // 0bc8 | or ecx, eax // 56 | push esi // 57 | push edi // 7529 | jne 0x2b $sequence_15 = { 83c201 8955e0 83d600 8975e4 } // n = 4, score = 300 // 83c201 | add edx, 1 // 8955e0 | mov dword ptr [ebp - 0x20], edx // 83d600 | adc esi, 0 // 8975e4 | mov dword ptr [ebp - 0x1c], esi $sequence_16 = { 8b45e4 50 51 52 56 } // n = 5, score = 300 // 8b45e4 | mov eax, dword ptr [ebp - 0x1c] // 50 | push eax // 51 | push ecx // 52 | push edx // 56 | push esi $sequence_17 = { 6a04 8d4310 50 6a06 } // n = 4, score = 300 // 6a04 | push 4 // 8d4310 | lea eax, [ebx + 0x10] // 50 | push eax // 6a06 | push 6 $sequence_18 = { 660fef4de0 0f294dc0 0f284dd0 50 } // n = 4, score = 300 // 660fef4de0 | pxor xmm1, xmmword ptr [ebp - 0x20] // 0f294dc0 | movaps xmmword ptr [ebp - 0x40], xmm1 // 0f284dd0 | movaps xmm1, xmmword ptr [ebp - 0x30] // 50 | push eax $sequence_19 = { 8b4598 03d0 8b4d9c 13f1 83c201 } // n = 5, score = 300 // 8b4598 | mov eax, dword ptr [ebp - 0x68] // 03d0 | add edx, eax // 8b4d9c | mov ecx, dword ptr [ebp - 0x64] // 13f1 | adc esi, ecx // 83c201 | add edx, 1 condition: 7 of them and filesize < 3670016 }