According to Mandiant, this is a tunneler, likely based on an open-source Socks4a proxy, that communicates using Azure cloud infrastructure.
rule win_lightrail_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.lightrail." 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.lightrail" 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 = { b931ad0231 e8???????? 48894330 4885c0 0f8486000000 } // n = 5, score = 100 // b931ad0231 | xor ecx, ecx // e8???????? | // 48894330 | dec eax // 4885c0 | mov dword ptr [esp + 0x50], eax // 0f8486000000 | inc ebp $sequence_1 = { 48d3c8 4533c0 33d2 33c9 ff15???????? 488d0d505b0100 eb0c } // n = 7, score = 100 // 48d3c8 | je 0x1d96 // 4533c0 | mov edx, 0xc86413d4 // 33d2 | mov ecx, 0xd34c7039 // 33c9 | dec eax // ff15???????? | // 488d0d505b0100 | mov dword ptr [ebx + 0xb8], eax // eb0c | dec eax $sequence_2 = { 488d152c7d0000 b914000000 e8???????? 4885c0 7452 } // n = 5, score = 100 // 488d152c7d0000 | dec ebp // b914000000 | mov ecx, dword ptr [edi + eax*8 + 0x1a710] // e8???????? | // 4885c0 | dec ecx // 7452 | mov esi, ebx $sequence_3 = { 0f84eb000000 4885c0 0f85e4000000 4d3bc1 0f84d1000000 8b7500 498b9cf700a10100 } // n = 7, score = 100 // 0f84eb000000 | dec eax // 4885c0 | lea ecx, [0xf677] // 0f85e4000000 | and eax, 0x3f // 4d3bc1 | dec ebp // 0f84d1000000 | mov ebp, esp // 8b7500 | dec ecx // 498b9cf700a10100 | sar ebp, 6 $sequence_4 = { 8b0c8e 4903ca 483bcf 721a 438b84168c000000 } // n = 5, score = 100 // 8b0c8e | lea edx, [esp + 0x48] // 4903ca | dec eax // 483bcf | test eax, eax // 721a | je 0x47f // 438b84168c000000 | nop $sequence_5 = { 746d 4533c9 8d5772 4533c0 488bc8 ff93c8020000 } // n = 6, score = 100 // 746d | je 0x36f // 4533c9 | xor edx, edx // 8d5772 | mov word ptr [esp + 0x20], 0x2e // 4533c0 | inc ecx // 488bc8 | mov eax, 0x104 // ff93c8020000 | dec eax $sequence_6 = { 442bc9 4183f90f 7779 428b8c8ef89a0000 4803ce ffe1 } // n = 6, score = 100 // 442bc9 | dec ecx // 4183f90f | mov ecx, esi // 7779 | inc esp // 428b8c8ef89a0000 | mov eax, ebx // 4803ce | dec eax // ffe1 | lea edx, [0x76d0] $sequence_7 = { f2410f1004c1 488d15d6860000 f20f1014c2 f20f1025???????? } // n = 4, score = 100 // f2410f1004c1 | dec ebp // 488d15d6860000 | cmp dword ptr [eax + ecx*8 + 0x10], edx // f20f1014c2 | je 0x1075 // f20f1025???????? | $sequence_8 = { ff9778020000 4c63f0 4983feff 0f84ef000000 } // n = 4, score = 100 // ff9778020000 | dec ecx // 4c63f0 | mov ebp, eax // 4983feff | dec esp // 0f84ef000000 | mov ebp, edx $sequence_9 = { 8b542430 48891401 488d0d4ab90000 e8???????? } // n = 4, score = 100 // 8b542430 | inc ebp // 48891401 | mov ecx, ebx // 488d0d4ab90000 | dec ebp // e8???????? | condition: 7 of them and filesize < 249856 }
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