Actor(s): APT41, Aurora Panda, Leviathan
a backdoor that obfuscates its communications as normal traffic to legitimate websites such as Github and Microsoft's Technet portal.
rule win_blackcoffee_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.blackcoffee." 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.blackcoffee" malpedia_rule_date = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" 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 = { 6a1c 6a40 ff15???????? 8bf0 33c0 50 } // n = 6, score = 200 // 6a1c | push 0x1c // 6a40 | push 0x40 // ff15???????? | // 8bf0 | mov esi, eax // 33c0 | xor eax, eax // 50 | push eax $sequence_1 = { 53 56 57 8b38 681c010000 6a40 } // n = 6, score = 200 // 53 | push ebx // 56 | push esi // 57 | push edi // 8b38 | mov edi, dword ptr [eax] // 681c010000 | push 0x11c // 6a40 | push 0x40 $sequence_2 = { 56 894604 e8???????? ff36 } // n = 4, score = 200 // 56 | push esi // 894604 | mov dword ptr [esi + 4], eax // e8???????? | // ff36 | push dword ptr [esi] $sequence_3 = { 57 ff15???????? 8bd8 3bdf 747a } // n = 5, score = 200 // 57 | push edi // ff15???????? | // 8bd8 | mov ebx, eax // 3bdf | cmp ebx, edi // 747a | je 0x7c $sequence_4 = { 8d85f0feffff 8d7718 8945f8 6a04 895efc } // n = 5, score = 200 // 8d85f0feffff | lea eax, [ebp - 0x110] // 8d7718 | lea esi, [edi + 0x18] // 8945f8 | mov dword ptr [ebp - 8], eax // 6a04 | push 4 // 895efc | mov dword ptr [esi - 4], ebx $sequence_5 = { f3ab 8d8568ffffff 33f6 50 } // n = 4, score = 200 // f3ab | rep stosd dword ptr es:[edi], eax // 8d8568ffffff | lea eax, [ebp - 0x98] // 33f6 | xor esi, esi // 50 | push eax $sequence_6 = { 50 894508 e8???????? 8b1d???????? 8945f4 } // n = 5, score = 200 // 50 | push eax // 894508 | mov dword ptr [ebp + 8], eax // e8???????? | // 8b1d???????? | // 8945f4 | mov dword ptr [ebp - 0xc], eax $sequence_7 = { c7460407100680 8b45fc 89460c c70614000000 } // n = 4, score = 200 // c7460407100680 | mov dword ptr [esi + 4], 0x80061007 // 8b45fc | mov eax, dword ptr [ebp - 4] // 89460c | mov dword ptr [esi + 0xc], eax // c70614000000 | mov dword ptr [esi], 0x14 $sequence_8 = { 8bd8 53 e8???????? 89443e04 5f 8bc3 5e } // n = 7, score = 200 // 8bd8 | mov ebx, eax // 53 | push ebx // e8???????? | // 89443e04 | mov dword ptr [esi + edi + 4], eax // 5f | pop edi // 8bc3 | mov eax, ebx // 5e | pop esi $sequence_9 = { 750b ff15???????? 89460c eb28 57 57 } // n = 6, score = 200 // 750b | jne 0xd // ff15???????? | // 89460c | mov dword ptr [esi + 0xc], eax // eb28 | jmp 0x2a // 57 | push edi // 57 | push edi condition: 7 of them and filesize < 118784 }
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