Also known as Wacatac ransomware due to its .wctc extension.
rule win_deathransom_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.deathransom." 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.deathransom" 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 = { 8b55d8 33c3 03c1 81c216c1a419 03d0 8bcf 0155ec } // n = 7, score = 100 // 8b55d8 | mov edx, dword ptr [ebp - 0x28] // 33c3 | xor eax, ebx // 03c1 | add eax, ecx // 81c216c1a419 | add edx, 0x19a4c116 // 03d0 | add edx, eax // 8bcf | mov ecx, edi // 0155ec | add dword ptr [ebp - 0x14], edx $sequence_1 = { 03d1 c1c007 0355a8 8bcf c1c90b 33c8 8955d8 } // n = 7, score = 100 // 03d1 | add edx, ecx // c1c007 | rol eax, 7 // 0355a8 | add edx, dword ptr [ebp - 0x58] // 8bcf | mov ecx, edi // c1c90b | ror ecx, 0xb // 33c8 | xor ecx, eax // 8955d8 | mov dword ptr [ebp - 0x28], edx $sequence_2 = { 742d 8b45f8 ba20000000 2bd6 8bca d3e8 8bce } // n = 7, score = 100 // 742d | je 0x2f // 8b45f8 | mov eax, dword ptr [ebp - 8] // ba20000000 | mov edx, 0x20 // 2bd6 | sub edx, esi // 8bca | mov ecx, edx // d3e8 | shr eax, cl // 8bce | mov ecx, esi $sequence_3 = { 0f8278010000 8b5df4 8d4dd8 56 8bd3 837b0400 } // n = 6, score = 100 // 0f8278010000 | jb 0x17e // 8b5df4 | mov ebx, dword ptr [ebp - 0xc] // 8d4dd8 | lea ecx, [ebp - 0x28] // 56 | push esi // 8bd3 | mov edx, ebx // 837b0400 | cmp dword ptr [ebx + 4], 0 $sequence_4 = { c3 83f802 7546 6820020000 6a08 c745fc20020000 ff15???????? } // n = 7, score = 100 // c3 | ret // 83f802 | cmp eax, 2 // 7546 | jne 0x48 // 6820020000 | push 0x220 // 6a08 | push 8 // c745fc20020000 | mov dword ptr [ebp - 4], 0x220 // ff15???????? | $sequence_5 = { 8d8d90fdffff e8???????? 8d8d90fdffff e8???????? 8d8d90fdffff e8???????? 6a50 } // n = 7, score = 100 // 8d8d90fdffff | lea ecx, [ebp - 0x270] // e8???????? | // 8d8d90fdffff | lea ecx, [ebp - 0x270] // e8???????? | // 8d8d90fdffff | lea ecx, [ebp - 0x270] // e8???????? | // 6a50 | push 0x50 $sequence_6 = { 0b7de4 237ddc 8b55f4 0bf8 897de0 8bc6 014de0 } // n = 7, score = 100 // 0b7de4 | or edi, dword ptr [ebp - 0x1c] // 237ddc | and edi, dword ptr [ebp - 0x24] // 8b55f4 | mov edx, dword ptr [ebp - 0xc] // 0bf8 | or edi, eax // 897de0 | mov dword ptr [ebp - 0x20], edi // 8bc6 | mov eax, esi // 014de0 | add dword ptr [ebp - 0x20], ecx $sequence_7 = { 8b45dc 8bc8 0155e8 c1c00a } // n = 4, score = 100 // 8b45dc | mov eax, dword ptr [ebp - 0x24] // 8bc8 | mov ecx, eax // 0155e8 | add dword ptr [ebp - 0x18], edx // c1c00a | rol eax, 0xa $sequence_8 = { 85c9 0f95c0 2bc8 33c0 c1e905 } // n = 5, score = 100 // 85c9 | test ecx, ecx // 0f95c0 | setne al // 2bc8 | sub ecx, eax // 33c0 | xor eax, eax // c1e905 | shr ecx, 5 $sequence_9 = { c1e810 884311 8bc1 c1e808 884312 884b13 8b4f1c } // n = 7, score = 100 // c1e810 | shr eax, 0x10 // 884311 | mov byte ptr [ebx + 0x11], al // 8bc1 | mov eax, ecx // c1e808 | shr eax, 8 // 884312 | mov byte ptr [ebx + 0x12], al // 884b13 | mov byte ptr [ebx + 0x13], cl // 8b4f1c | mov ecx, dword ptr [edi + 0x1c] condition: 7 of them and filesize < 133120 }
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