rule win_warmcookie_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-09-17" version = "1" description = "Detects win.warmcookie." 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.warmcookie" 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 = { c744242880000000 c744242003000000 41b900000000 41b807000000 ba00000080 } // n = 5, score = 900 // c744242880000000 | dec ecx // c744242003000000 | mov eax, ebx // 41b900000000 | dec eax // 41b807000000 | mov ecx, ebx // ba00000080 | dec ecx $sequence_1 = { 41b902000000 41b800000000 ba00000000 4889c1 } // n = 4, score = 900 // 41b902000000 | inc ecx // 41b800000000 | mov eax, 7 // ba00000000 | mov edx, 0x80000000 // 4889c1 | dec eax $sequence_2 = { 899c2498000000 488d5e02 48896c2470 8944242c 48b8fffffffffdffffff 4889842480000000 31c0 } // n = 7, score = 900 // 899c2498000000 | mov eax, 0 // 488d5e02 | mov edx, 0 // 48896c2470 | dec eax // 8944242c | mov ecx, eax // 48b8fffffffffdffffff | dec eax // 4889842480000000 | mov dword ptr [esp + 0x30], 0 // 31c0 | mov dword ptr [esp + 0x28], 0x80 $sequence_3 = { 83e830 6683f809 0f8709060000 4183fe03 } // n = 4, score = 900 // 83e830 | mov eax, 7 // 6683f809 | mov edx, 0x80000000 // 0f8709060000 | inc ecx // 4183fe03 | mov ecx, 0 $sequence_4 = { 415c c3 55 4157 4156 4155 } // n = 6, score = 900 // 415c | inc ecx // c3 | mov eax, 7 // 55 | mov edx, 0x80000000 // 4157 | dec eax // 4156 | mov ecx, eax // 4155 | dec eax $sequence_5 = { 4181f80080ffff 7470 8b4c2448 4889c2 } // n = 4, score = 900 // 4181f80080ffff | mov dword ptr [esp + 0x20], 3 // 7470 | inc ecx // 8b4c2448 | mov ecx, 0 // 4889c2 | inc ecx $sequence_6 = { 0f8e1bffffff 01d0 89430c e9???????? 4157 4156 } // n = 6, score = 900 // 0f8e1bffffff | dec eax // 01d0 | mov ecx, eax // 89430c | inc ecx // e9???????? | // 4157 | mov ecx, 2 // 4156 | inc ecx $sequence_7 = { e8???????? 3dff2f0000 0f97c0 0fb6c0 } // n = 4, score = 700 // e8???????? | // 3dff2f0000 | cmp eax, 0x2fff // 0f97c0 | seta al // 0fb6c0 | movzx eax, al $sequence_8 = { ba19000000 488b4c2438 ff15???????? 85c0 } // n = 4, score = 700 // ba19000000 | mov edx, 0x19 // 488b4c2438 | dec eax // ff15???????? | // 85c0 | mov ecx, dword ptr [esp + 0x38] $sequence_9 = { ff5010 b9e8030000 ff15???????? 83ef01 } // n = 4, score = 600 // ff5010 | std // b9e8030000 | inc ecx // ff15???????? | // 83ef01 | cmp eax, 0xffff8000 $sequence_10 = { 85c0 7409 488b442428 48c1e814 } // n = 4, score = 600 // 85c0 | dec eax // 7409 | mov ecx, eax // 488b442428 | call ebx // 48c1e814 | test eax, eax $sequence_11 = { 488d4c0301 4801c9 e8???????? 4889c3 4885c0 } // n = 5, score = 600 // 488d4c0301 | add ecx, esi // 4801c9 | mov dword ptr [esi + 0x20], edi // e8???????? | // 4889c3 | dec eax // 4885c0 | mov ebx, dword ptr [esp + 0x60] $sequence_12 = { ff15???????? 25ff0f0000 8d88b80b0000 ff15???????? } // n = 4, score = 600 // ff15???????? | // 25ff0f0000 | dec eax // 8d88b80b0000 | shr eax, 0x14 // ff15???????? | $sequence_13 = { ba18000000 4889c1 ffd3 85c0 } // n = 4, score = 600 // ba18000000 | cmp eax, 0x2fff // 4889c1 | seta al // ffd3 | movzx eax, al // 85c0 | mov edx, 0x18 $sequence_14 = { 488b01 ff9080000000 85c0 7815 } // n = 4, score = 600 // 488b01 | test eax, eax // ff9080000000 | je 0xb // 85c0 | dec eax // 7815 | mov eax, dword ptr [esp + 0x28] $sequence_15 = { 6642837c40fe00 75f3 4b8d1c00 4889d9 e8???????? 4989d8 } // n = 6, score = 500 // 6642837c40fe00 | and eax, 0xfff // 75f3 | lea ecx, [eax + 0xbb8] // 4b8d1c00 | dec eax // 4889d9 | mov eax, ebp // e8???????? | // 4989d8 | $sequence_16 = { 4889e8 f0480fb13b 4885c0 75e2 488b3d???????? 31ed } // n = 6, score = 500 // 4889e8 | dec eax // f0480fb13b | mov eax, dword ptr [ecx] // 4885c0 | call dword ptr [eax + 0x80] // 75e2 | test eax, eax // 488b3d???????? | // 31ed | js 0x1f $sequence_17 = { 488d542470 b901010000 ff15???????? 85c0 } // n = 4, score = 300 // 488d542470 | inc ecx // b901010000 | mov ecx, 0 // ff15???????? | // 85c0 | inc ecx $sequence_18 = { 488b5c2460 8d4801 e8???????? 4c8bf8 } // n = 4, score = 300 // 488b5c2460 | cmp eax, 0x2fff // 8d4801 | seta al // e8???????? | // 4c8bf8 | cmp eax, 0x2fff $sequence_19 = { ff15???????? 488be8 4883f8ff 7444 4533c9 } // n = 5, score = 300 // ff15???????? | // 488be8 | seta al // 4883f8ff | movzx eax, al // 7444 | test eax, eax // 4533c9 | je 0xb $sequence_20 = { 4b8d040b 4688441102 483d00010000 72c8 488b5c2408 488b742410 } // n = 6, score = 300 // 4b8d040b | mov eax, 7 // 4688441102 | mov edx, 0x80000000 // 483d00010000 | inc ecx // 72c8 | mov ecx, 0 // 488b5c2408 | inc ecx // 488b742410 | mov eax, 7 $sequence_21 = { 83f805 7c34 e8???????? 83f804 720c e8???????? 3d000f0000 } // n = 7, score = 300 // 83f805 | dec eax // 7c34 | mov eax, dword ptr [esp + 0x28] // e8???????? | // 83f804 | dec eax // 720c | shr eax, 0x14 // e8???????? | // 3d000f0000 | call dword ptr [eax + 0x10] $sequence_22 = { ff15???????? 85c0 75c2 85f6 740f } // n = 5, score = 300 // ff15???????? | // 85c0 | sub esp, 0x28 // 75c2 | cmp eax, 0x2fff // 85f6 | seta al // 740f | movzx eax, al $sequence_23 = { 8bcf 498bd6 4803ce e8???????? 897e20 } // n = 5, score = 300 // 8bcf | mov edx, 0x80000000 // 498bd6 | dec eax // 4803ce | mov ecx, eax // e8???????? | // 897e20 | dec eax condition: 7 of them and filesize < 331776 }