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 = "2023-12-06" 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 = "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 = { 8d85f0feffff 50 8bcf ff15???????? 8b08 8b4904 } // n = 6, score = 100 // 8d85f0feffff | lea eax, [ebp - 0x110] // 50 | push eax // 8bcf | mov ecx, edi // ff15???????? | // 8b08 | mov ecx, dword ptr [eax] // 8b4904 | mov ecx, dword ptr [ecx + 4] $sequence_1 = { 745f 6a30 c7460800000000 e8???????? 83c404 85c0 } // n = 6, score = 100 // 745f | je 0x61 // 6a30 | push 0x30 // c7460800000000 | mov dword ptr [esi + 8], 0 // e8???????? | // 83c404 | add esp, 4 // 85c0 | test eax, eax $sequence_2 = { 0fbe56ff 4e 51 52 57 ffd3 83c40c } // n = 7, score = 100 // 0fbe56ff | movsx edx, byte ptr [esi - 1] // 4e | dec esi // 51 | push ecx // 52 | push edx // 57 | push edi // ffd3 | call ebx // 83c40c | add esp, 0xc $sequence_3 = { e8???????? 83c408 8bc8 ff15???????? 397314 7204 } // n = 6, score = 100 // e8???????? | // 83c408 | add esp, 8 // 8bc8 | mov ecx, eax // ff15???????? | // 397314 | cmp dword ptr [ebx + 0x14], esi // 7204 | jb 6 $sequence_4 = { 8d4f04 894e30 894e34 8d4708 8d4d10 894610 894614 } // n = 7, score = 100 // 8d4f04 | lea ecx, [edi + 4] // 894e30 | mov dword ptr [esi + 0x30], ecx // 894e34 | mov dword ptr [esi + 0x34], ecx // 8d4708 | lea eax, [edi + 8] // 8d4d10 | lea ecx, [ebp + 0x10] // 894610 | mov dword ptr [esi + 0x10], eax // 894614 | mov dword ptr [esi + 0x14], eax $sequence_5 = { 68???????? 64a100000000 50 81ecec050000 a1???????? 33c5 8945ec } // n = 7, score = 100 // 68???????? | // 64a100000000 | mov eax, dword ptr fs:[0] // 50 | push eax // 81ecec050000 | sub esp, 0x5ec // a1???????? | // 33c5 | xor eax, ebp // 8945ec | mov dword ptr [ebp - 0x14], eax $sequence_6 = { 83c420 8d14c500000000 2bd0 8b06 5b 8d0cd0 } // n = 6, score = 100 // 83c420 | add esp, 0x20 // 8d14c500000000 | lea edx, [eax*8] // 2bd0 | sub edx, eax // 8b06 | mov eax, dword ptr [esi] // 5b | pop ebx // 8d0cd0 | lea ecx, [eax + edx*8] $sequence_7 = { 03c2 894508 753d 8b4604 8b0e 3bc8 0f8466010000 } // n = 7, score = 100 // 03c2 | add eax, edx // 894508 | mov dword ptr [ebp + 8], eax // 753d | jne 0x3f // 8b4604 | mov eax, dword ptr [esi + 4] // 8b0e | mov ecx, dword ptr [esi] // 3bc8 | cmp ecx, eax // 0f8466010000 | je 0x16c $sequence_8 = { 0b0b 010b 0b0b 0b0b 0b0b 0b0b 0b0b } // n = 7, score = 100 // 0b0b | or ecx, dword ptr [ebx] // 010b | add dword ptr [ebx], ecx // 0b0b | or ecx, dword ptr [ebx] // 0b0b | or ecx, dword ptr [ebx] // 0b0b | or ecx, dword ptr [ebx] // 0b0b | or ecx, dword ptr [ebx] // 0b0b | or ecx, dword ptr [ebx] $sequence_9 = { 33db 8bc7 8bf1 c745e80f000000 895de4 885dd4 8d5001 } // n = 7, score = 100 // 33db | xor ebx, ebx // 8bc7 | mov eax, edi // 8bf1 | mov esi, ecx // c745e80f000000 | mov dword ptr [ebp - 0x18], 0xf // 895de4 | mov dword ptr [ebp - 0x1c], ebx // 885dd4 | mov byte ptr [ebp - 0x2c], bl // 8d5001 | lea edx, [eax + 1] condition: 7 of them and filesize < 424960 }
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