Mandiant associates this with UNC4191, this malware is a launcher for NCAT to establish a reverse tunnel.
rule win_bluehaze_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-01-05" version = "1" description = "Detects win.bluehaze." 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.bluehaze" 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 = { 85ff 7405 8b4dec 890f 83c704 897dd8 3b5604 } // n = 7, score = 100 // 85ff | test edi, edi // 7405 | je 7 // 8b4dec | mov ecx, dword ptr [ebp - 0x14] // 890f | mov dword ptr [edi], ecx // 83c704 | add edi, 4 // 897dd8 | mov dword ptr [ebp - 0x28], edi // 3b5604 | cmp edx, dword ptr [esi + 4] $sequence_1 = { 894704 8b4804 8901 837dcc10 c745fcffffffff 720c } // n = 6, score = 100 // 894704 | mov dword ptr [edi + 4], eax // 8b4804 | mov ecx, dword ptr [eax + 4] // 8901 | mov dword ptr [ecx], eax // 837dcc10 | cmp dword ptr [ebp - 0x34], 0x10 // c745fcffffffff | mov dword ptr [ebp - 4], 0xffffffff // 720c | jb 0xe $sequence_2 = { 51 c745fc00000000 e8???????? 83c408 837de810 720c 8b55d4 } // n = 7, score = 100 // 51 | push ecx // c745fc00000000 | mov dword ptr [ebp - 4], 0 // e8???????? | // 83c408 | add esp, 8 // 837de810 | cmp dword ptr [ebp - 0x18], 0x10 // 720c | jb 0xe // 8b55d4 | mov edx, dword ptr [ebp - 0x2c] $sequence_3 = { c706???????? 8bc6 5e 8be5 5d c3 8d45fc } // n = 7, score = 100 // c706???????? | // 8bc6 | mov eax, esi // 5e | pop esi // 8be5 | mov esp, ebp // 5d | pop ebp // c3 | ret // 8d45fc | lea eax, [ebp - 4] $sequence_4 = { 33d2 eb02 8b10 8b4518 85c0 740c } // n = 6, score = 100 // 33d2 | xor edx, edx // eb02 | jmp 4 // 8b10 | mov edx, dword ptr [eax] // 8b4518 | mov eax, dword ptr [ebp + 0x18] // 85c0 | test eax, eax // 740c | je 0xe $sequence_5 = { 03ce 51 8b4b6c 57 51 ff15???????? } // n = 6, score = 100 // 03ce | add ecx, esi // 51 | push ecx // 8b4b6c | mov ecx, dword ptr [ebx + 0x6c] // 57 | push edi // 51 | push ecx // ff15???????? | $sequence_6 = { c706???????? e8???????? 6a30 c745fc00000000 c7462000000000 e8???????? 83c404 } // n = 7, score = 100 // c706???????? | // e8???????? | // 6a30 | push 0x30 // c745fc00000000 | mov dword ptr [ebp - 4], 0 // c7462000000000 | mov dword ptr [esi + 0x20], 0 // e8???????? | // 83c404 | add esp, 4 $sequence_7 = { 53 8d9564feffff 52 8d8dd4feffff e8???????? 8b7010 838d20feffff01 } // n = 7, score = 100 // 53 | push ebx // 8d9564feffff | lea edx, [ebp - 0x19c] // 52 | push edx // 8d8dd4feffff | lea ecx, [ebp - 0x12c] // e8???????? | // 8b7010 | mov esi, dword ptr [eax + 0x10] // 838d20feffff01 | or dword ptr [ebp - 0x1e0], 1 $sequence_8 = { c747140f000000 895f10 881f 833e10 7315 8b56fc } // n = 6, score = 100 // c747140f000000 | mov dword ptr [edi + 0x14], 0xf // 895f10 | mov dword ptr [edi + 0x10], ebx // 881f | mov byte ptr [edi], bl // 833e10 | cmp dword ptr [esi], 0x10 // 7315 | jae 0x17 // 8b56fc | mov edx, dword ptr [esi - 4] $sequence_9 = { e8???????? 83c404 c785ccfeffff0f000000 899dc8feffff 889db8feffff c645fc03 39b578feffff } // n = 7, score = 100 // e8???????? | // 83c404 | add esp, 4 // c785ccfeffff0f000000 | mov dword ptr [ebp - 0x134], 0xf // 899dc8feffff | mov dword ptr [ebp - 0x138], ebx // 889db8feffff | mov byte ptr [ebp - 0x148], bl // c645fc03 | mov byte ptr [ebp - 4], 3 // 39b578feffff | cmp dword ptr [ebp - 0x188], esi condition: 7 of them and filesize < 424960 }
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