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 = "2023-01-25" 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 = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { 55 8bec 56 8b7508 8b06 8b5014 68bc020000 } // n = 7, score = 100 // 55 | push ebp // 8bec | mov ebp, esp // 56 | push esi // 8b7508 | mov esi, dword ptr [ebp + 8] // 8b06 | mov eax, dword ptr [esi] // 8b5014 | mov edx, dword ptr [eax + 0x14] // 68bc020000 | push 0x2bc $sequence_1 = { 8b5104 83c404 894208 eb5d 894104 8b0f 8908 } // n = 7, score = 100 // 8b5104 | mov edx, dword ptr [ecx + 4] // 83c404 | add esp, 4 // 894208 | mov dword ptr [edx + 8], eax // eb5d | jmp 0x5f // 894104 | mov dword ptr [ecx + 4], eax // 8b0f | mov ecx, dword ptr [edi] // 8908 | mov dword ptr [eax], ecx $sequence_2 = { 720f 8b8d54ffffff 51 e8???????? 83c404 8d8d84feffff c645fc00 } // n = 7, score = 100 // 720f | jb 0x11 // 8b8d54ffffff | mov ecx, dword ptr [ebp - 0xac] // 51 | push ecx // e8???????? | // 83c404 | add esp, 4 // 8d8d84feffff | lea ecx, [ebp - 0x17c] // c645fc00 | mov byte ptr [ebp - 4], 0 $sequence_3 = { f6855cffffff01 c645fc08 7411 8b952cffffff 8b02 50 e8???????? } // n = 7, score = 100 // f6855cffffff01 | test byte ptr [ebp - 0xa4], 1 // c645fc08 | mov byte ptr [ebp - 4], 8 // 7411 | je 0x13 // 8b952cffffff | mov edx, dword ptr [ebp - 0xd4] // 8b02 | mov eax, dword ptr [edx] // 50 | push eax // e8???????? | $sequence_4 = { 8b10 6a01 ffd2 8d4e2c e8???????? 8b7e2c 57 } // n = 7, score = 100 // 8b10 | mov edx, dword ptr [eax] // 6a01 | push 1 // ffd2 | call edx // 8d4e2c | lea ecx, [esi + 0x2c] // e8???????? | // 8b7e2c | mov edi, dword ptr [esi + 0x2c] // 57 | push edi $sequence_5 = { 8bc8 8b01 385845 74f7 898d44ffffff eb2b 8b4204 } // n = 7, score = 100 // 8bc8 | mov ecx, eax // 8b01 | mov eax, dword ptr [ecx] // 385845 | cmp byte ptr [eax + 0x45], bl // 74f7 | je 0xfffffff9 // 898d44ffffff | mov dword ptr [ebp - 0xbc], ecx // eb2b | jmp 0x2d // 8b4204 | mov eax, dword ptr [edx + 4] $sequence_6 = { 894008 8b4604 c6402c01 8b4e04 c6412d01 eb2b 8d55f0 } // n = 7, score = 100 // 894008 | mov dword ptr [eax + 8], eax // 8b4604 | mov eax, dword ptr [esi + 4] // c6402c01 | mov byte ptr [eax + 0x2c], 1 // 8b4e04 | mov ecx, dword ptr [esi + 4] // c6412d01 | mov byte ptr [ecx + 0x2d], 1 // eb2b | jmp 0x2d // 8d55f0 | lea edx, [ebp - 0x10] $sequence_7 = { 8b4510 6aff 8d4e38 53 c741140f000000 895910 50 } // n = 7, score = 100 // 8b4510 | mov eax, dword ptr [ebp + 0x10] // 6aff | push -1 // 8d4e38 | lea ecx, [esi + 0x38] // 53 | push ebx // c741140f000000 | mov dword ptr [ecx + 0x14], 0xf // 895910 | mov dword ptr [ecx + 0x10], ebx // 50 | push eax $sequence_8 = { bf01000000 eb1f 397590 741d 3bce 7419 80fb78 } // n = 7, score = 100 // bf01000000 | mov edi, 1 // eb1f | jmp 0x21 // 397590 | cmp dword ptr [ebp - 0x70], esi // 741d | je 0x1f // 3bce | cmp ecx, esi // 7419 | je 0x1b // 80fb78 | cmp bl, 0x78 $sequence_9 = { 8bc8 e8???????? eb02 33c0 894628 8bc6 8b4df4 } // n = 7, score = 100 // 8bc8 | mov ecx, eax // e8???????? | // eb02 | jmp 4 // 33c0 | xor eax, eax // 894628 | mov dword ptr [esi + 0x28], eax // 8bc6 | mov eax, esi // 8b4df4 | mov ecx, dword ptr [ebp - 0xc] condition: 7 of them and filesize < 424960 }
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