Actor(s): Lucky Cat
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rule win_lowzero_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.lowzero." 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.lowzero" malpedia_rule_date = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { 57 e8???????? 59 8975fc 8b45e0 8b0485601b4300 f644030401 } // n = 7, score = 100 // 57 | push edi // e8???????? | // 59 | pop ecx // 8975fc | mov dword ptr [ebp - 4], esi // 8b45e0 | mov eax, dword ptr [ebp - 0x20] // 8b0485601b4300 | mov eax, dword ptr [eax*4 + 0x431b60] // f644030401 | test byte ptr [ebx + eax + 4], 1 $sequence_1 = { 8bf0 c1ff05 83e61f c1e606 8b0cbd601b4300 } // n = 5, score = 100 // 8bf0 | mov esi, eax // c1ff05 | sar edi, 5 // 83e61f | and esi, 0x1f // c1e606 | shl esi, 6 // 8b0cbd601b4300 | mov ecx, dword ptr [edi*4 + 0x431b60] $sequence_2 = { 7309 8b04c518dc4000 5d c3 33c0 5d c3 } // n = 7, score = 100 // 7309 | jae 0xb // 8b04c518dc4000 | mov eax, dword ptr [eax*8 + 0x40dc18] // 5d | pop ebp // c3 | ret // 33c0 | xor eax, eax // 5d | pop ebp // c3 | ret $sequence_3 = { 50 8b8528e5ffff 8b0485601b4300 ff3401 ff15???????? 8bb540e5ffff 8bbd34e5ffff } // n = 7, score = 100 // 50 | push eax // 8b8528e5ffff | mov eax, dword ptr [ebp - 0x1ad8] // 8b0485601b4300 | mov eax, dword ptr [eax*4 + 0x431b60] // ff3401 | push dword ptr [ecx + eax] // ff15???????? | // 8bb540e5ffff | mov esi, dword ptr [ebp - 0x1ac0] // 8bbd34e5ffff | mov edi, dword ptr [ebp - 0x1acc] $sequence_4 = { 8b8d24e5ffff 50 8b8528e5ffff 8b0485601b4300 } // n = 4, score = 100 // 8b8d24e5ffff | mov ecx, dword ptr [ebp - 0x1adc] // 50 | push eax // 8b8528e5ffff | mov eax, dword ptr [ebp - 0x1ad8] // 8b0485601b4300 | mov eax, dword ptr [eax*4 + 0x431b60] $sequence_5 = { 83e31f c1e306 8b0485601b4300 0fbe440304 83e001 7472 } // n = 6, score = 100 // 83e31f | and ebx, 0x1f // c1e306 | shl ebx, 6 // 8b0485601b4300 | mov eax, dword ptr [eax*4 + 0x431b60] // 0fbe440304 | movsx eax, byte ptr [ebx + eax + 4] // 83e001 | and eax, 1 // 7472 | je 0x74 $sequence_6 = { 3de4000000 7309 8b04c518dc4000 5d c3 } // n = 5, score = 100 // 3de4000000 | cmp eax, 0xe4 // 7309 | jae 0xb // 8b04c518dc4000 | mov eax, dword ptr [eax*8 + 0x40dc18] // 5d | pop ebp // c3 | ret $sequence_7 = { c1e106 8b0485601b4300 0fbe440804 83e040 5d c3 e8???????? } // n = 7, score = 100 // c1e106 | shl ecx, 6 // 8b0485601b4300 | mov eax, dword ptr [eax*4 + 0x431b60] // 0fbe440804 | movsx eax, byte ptr [eax + ecx + 4] // 83e040 | and eax, 0x40 // 5d | pop ebp // c3 | ret // e8???????? | $sequence_8 = { 8bf0 2bf1 8bcf f30f6f01 83c210 8d4910 } // n = 6, score = 100 // 8bf0 | mov esi, eax // 2bf1 | sub esi, ecx // 8bcf | mov ecx, edi // f30f6f01 | movdqu xmm0, xmmword ptr [ecx] // 83c210 | add edx, 0x10 // 8d4910 | lea ecx, [ecx + 0x10] $sequence_9 = { 8a441918 888180114100 41 ebe8 8975e4 81fe00010000 } // n = 6, score = 100 // 8a441918 | mov al, byte ptr [ecx + ebx + 0x18] // 888180114100 | mov byte ptr [ecx + 0x411180], al // 41 | inc ecx // ebe8 | jmp 0xffffffea // 8975e4 | mov dword ptr [ebp - 0x1c], esi // 81fe00010000 | cmp esi, 0x100 condition: 7 of them and filesize < 433152 }
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