Actor(s): APT28
According to CERT-UA, this is a malware developed using the C++ programming language. The main functional purpose is the production of screenshots.
rule win_slimagent_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.slimagent." 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.slimagent" malpedia_rule_date = "20260105" malpedia_hash = "19b79e7cab4eaf532122e5b45a77dd8f6bb5cc79" malpedia_version = "20251219" 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 = { 488bc2 488d0df5440200 0f57c0 48890b 488d5308 488d4808 0f1102 } // n = 7, score = 100 // 488bc2 | dec eax // 488d0df5440200 | mov edx, dword ptr [ebp - 0x38] // 0f57c0 | dec esp // 48890b | lea eax, [0x1fb4e] // 488d5308 | test eax, eax // 488d4808 | je 0x441 // 0f1102 | dec ecx $sequence_1 = { b801000000 874110 85c0 7427 8364244000 488d05d2a5feff 4889442448 } // n = 7, score = 100 // b801000000 | dec eax // 874110 | lea ecx, [ebp - 0x20] // 85c0 | nop // 7427 | dec eax // 8364244000 | mov eax, dword ptr [ebx] // 488d05d2a5feff | dec eax // 4889442448 | arpl word ptr [eax], cx $sequence_2 = { c3 4053 4883ec20 488d054bcf0200 488bd9 488901 f6c201 } // n = 7, score = 100 // c3 | mov edx, 0x56da4870 // 4053 | xchg eax, esi // 4883ec20 | int1 // 488d054bcf0200 | test dword ptr [ecx + 0x17], edi // 488bd9 | test eax, eax // 488901 | je 0xa3 // f6c201 | mov ecx, 2 $sequence_3 = { 0f1102 e8???????? 488d058c780200 488903 488bc3 4883c420 5b } // n = 7, score = 100 // 0f1102 | lea ecx, [0xd2e5] // e8???????? | // 488d058c780200 | vmulsd xmm0, xmm2, xmm2 // 488903 | vfmadd213sd xmm0, xmm3, xmm2 // 488bc3 | cmp ecx, 0xfffffc02 // 4883c420 | dec eax // 5b | lea edx, [0x12c34] $sequence_4 = { 66413b444b02 7515 4883c102 4883f90b 7415 0fb7044a 66413b044b } // n = 7, score = 100 // 66413b444b02 | lea ecx, [edx + 0x48] // 7515 | dec eax // 4883c102 | lea ecx, [edx + 0x80] // 4883f90b | dec eax // 7415 | lea ecx, [edx + 0x48] // 0fb7044a | pop ebp // 66413b044b | ret $sequence_5 = { 488d0c4f 41b810000000 488d15004c0400 e8???????? 6646892c77 eb7d 48c744242008000000 } // n = 7, score = 100 // 488d0c4f | dec ecx // 41b810000000 | mov edx, dword ptr [edi + edx*8 + 0x44fa0] // 488d15004c0400 | test eax, eax // e8???????? | // 6646892c77 | je 0xaa4 // eb7d | jns 0xa82 // 48c744242008000000 | dec eax $sequence_6 = { 4c8b83f0000000 498bc0 482bc1 483bd0 772f 488d3411 } // n = 6, score = 100 // 4c8b83f0000000 | dec eax // 498bc0 | test eax, eax // 482bc1 | jne 0xcfa // 483bd0 | dec eax // 772f | lea eax, [0x1d6ec] // 488d3411 | dec eax $sequence_7 = { 488bc2 48c1e83f 4803d0 4863c2 4869c880aefeff 488d0535240100 89531c } // n = 7, score = 100 // 488bc2 | mov eax, dword ptr [ebp - 0x20] // 48c1e83f | dec eax // 4803d0 | mov edx, dword ptr [ebp - 0x31] // 4863c2 | dec ecx // 4869c880aefeff | sub edx, esi // 488d0535240100 | dec ecx // 89531c | mov eax, esi $sequence_8 = { 4803fa 4d8bc6 33d2 488bcf e8???????? 42c6043700 eb0f } // n = 7, score = 100 // 4803fa | xor al, al // 4d8bc6 | dec eax // 33d2 | mov ecx, dword ptr [ebp + 0x50] // 488bcf | dec eax // e8???????? | // 42c6043700 | lea edx, [0x14a56] // eb0f | xor ebx, ebx $sequence_9 = { 48899fc8000000 668919 488d8fd8000000 4883bff000000008 7207 } // n = 5, score = 100 // 48899fc8000000 | inc esp // 668919 | mov ecx, eax // 488d8fd8000000 | mov ebx, eax // 4883bff000000008 | dec esp // 7207 | mov eax, dword ptr [edi + 8] condition: 7 of them and filesize < 769024 }
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