Actor(s): TA410
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rule win_lookback_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.lookback." 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.lookback" 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 = { 74c5 83f8ff 0f8427010000 8b0d???????? 8d442418 50 51 } // n = 7, score = 200 // 74c5 | je 0xffffffc7 // 83f8ff | cmp eax, -1 // 0f8427010000 | je 0x12d // 8b0d???????? | // 8d442418 | lea eax, [esp + 0x18] // 50 | push eax // 51 | push ecx $sequence_1 = { 8b7c241c 33ed 8b473c 8b443878 03c7 8b5024 } // n = 6, score = 200 // 8b7c241c | mov edi, dword ptr [esp + 0x1c] // 33ed | xor ebp, ebp // 8b473c | mov eax, dword ptr [edi + 0x3c] // 8b443878 | mov eax, dword ptr [eax + edi + 0x78] // 03c7 | add eax, edi // 8b5024 | mov edx, dword ptr [eax + 0x24] $sequence_2 = { 55 8bec 51 53 c745fc00000000 b801000000 } // n = 6, score = 200 // 55 | push ebp // 8bec | mov ebp, esp // 51 | push ecx // 53 | push ebx // c745fc00000000 | mov dword ptr [ebp - 4], 0 // b801000000 | mov eax, 1 $sequence_3 = { 8a442413 893d???????? 3c01 893d???????? 893d???????? 752e 33db } // n = 7, score = 200 // 8a442413 | mov al, byte ptr [esp + 0x13] // 893d???????? | // 3c01 | cmp al, 1 // 893d???????? | // 893d???????? | // 752e | jne 0x30 // 33db | xor ebx, ebx $sequence_4 = { 8bc8 6a01 83e103 6a02 f3a4 ff15???????? } // n = 6, score = 200 // 8bc8 | mov ecx, eax // 6a01 | push 1 // 83e103 | and ecx, 3 // 6a02 | push 2 // f3a4 | rep movsb byte ptr es:[edi], byte ptr [esi] // ff15???????? | $sequence_5 = { 5d 5b 59 c3 0594010000 8b08 894d00 } // n = 7, score = 200 // 5d | pop ebp // 5b | pop ebx // 59 | pop ecx // c3 | ret // 0594010000 | add eax, 0x194 // 8b08 | mov ecx, dword ptr [eax] // 894d00 | mov dword ptr [ebp], ecx $sequence_6 = { 7477 a1???????? 50 ff15???????? } // n = 4, score = 200 // 7477 | je 0x79 // a1???????? | // 50 | push eax // ff15???????? | $sequence_7 = { 03f7 833e00 742d 8bc6 } // n = 4, score = 200 // 03f7 | add esi, edi // 833e00 | cmp dword ptr [esi], 0 // 742d | je 0x2f // 8bc6 | mov eax, esi $sequence_8 = { 8b4df8 c1e010 5f 5e 0bc1 } // n = 5, score = 200 // 8b4df8 | mov ecx, dword ptr [ebp - 8] // c1e010 | shl eax, 0x10 // 5f | pop edi // 5e | pop esi // 0bc1 | or eax, ecx $sequence_9 = { 50 52 ff542420 85c0 751b a1???????? 50 } // n = 7, score = 200 // 50 | push eax // 52 | push edx // ff542420 | call dword ptr [esp + 0x20] // 85c0 | test eax, eax // 751b | jne 0x1d // a1???????? | // 50 | push eax condition: 7 of them and filesize < 131072 }
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