SystemBC is a proxy malware leveraging SOCKS5. Based on screenshots used in ads on a underground marketplace, Proofpoint decided to call it SystemBC.
SystemBC has been observed occasionally, but more pronounced since June 2019. First samples goes back to October 2018.
rule win_systembc_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-12-22" version = "1" description = "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.systembc" malpedia_rule_date = "20201222" malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130" malpedia_version = "20201023" 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 = { 7408 03bd1cf4ffff ebc1 2bbd20f4ffff } // n = 4, score = 800 // 7408 | je 0xa // 03bd1cf4ffff | add edi, dword ptr [ebp - 0xbe4] // ebc1 | jmp 0xffffffc3 // 2bbd20f4ffff | sub edi, dword ptr [ebp - 0xbe0] $sequence_1 = { eb08 8b543078 8b4c307c 8955ec } // n = 4, score = 800 // eb08 | jmp 0xa // 8b543078 | mov edx, dword ptr [eax + esi + 0x78] // 8b4c307c | mov ecx, dword ptr [eax + esi + 0x7c] // 8955ec | mov dword ptr [ebp - 0x14], edx $sequence_2 = { 64a130000000 8b400c 8b700c 8b5810 8b36 8b7e30 33c9 } // n = 7, score = 800 // 64a130000000 | mov eax, dword ptr fs:[0x30] // 8b400c | mov eax, dword ptr [eax + 0xc] // 8b700c | mov esi, dword ptr [eax + 0xc] // 8b5810 | mov ebx, dword ptr [eax + 0x10] // 8b36 | mov esi, dword ptr [esi] // 8b7e30 | mov edi, dword ptr [esi + 0x30] // 33c9 | xor ecx, ecx $sequence_3 = { 50 6805000020 ffb530f4ffff 68???????? e8???????? } // n = 5, score = 800 // 50 | push eax // 6805000020 | push 0x20000005 // ffb530f4ffff | push dword ptr [ebp - 0xbd0] // 68???????? | // e8???????? | $sequence_4 = { 8bcf 8dbd68feffff f3a4 c647ff00 8d8568feffff 50 e8???????? } // n = 7, score = 800 // 8bcf | mov ecx, edi // 8dbd68feffff | lea edi, [ebp - 0x198] // f3a4 | rep movsb byte ptr es:[edi], byte ptr [esi] // c647ff00 | mov byte ptr [edi - 1], 0 // 8d8568feffff | lea eax, [ebp - 0x198] // 50 | push eax // e8???????? | $sequence_5 = { 68???????? 50 e8???????? ffd0 6a00 } // n = 5, score = 800 // 68???????? | // 50 | push eax // e8???????? | // ffd0 | call eax // 6a00 | push 0 $sequence_6 = { e8???????? ffd0 6a00 6a00 6a00 6a00 ffb530f4ffff } // n = 7, score = 800 // e8???????? | // ffd0 | call eax // 6a00 | push 0 // 6a00 | push 0 // 6a00 | push 0 // 6a00 | push 0 // ffb530f4ffff | push dword ptr [ebp - 0xbd0] $sequence_7 = { 50 ffd2 8b85bcfbffff 8b08 8b5108 50 ffd2 } // n = 7, score = 800 // 50 | push eax // ffd2 | call edx // 8b85bcfbffff | mov eax, dword ptr [ebp - 0x444] // 8b08 | mov ecx, dword ptr [eax] // 8b5108 | mov edx, dword ptr [ecx + 8] // 50 | push eax // ffd2 | call edx $sequence_8 = { 55 8bec 53 57 56 ff7508 } // n = 6, score = 800 // 55 | push ebp // 8bec | mov ebp, esp // 53 | push ebx // 57 | push edi // 56 | push esi // ff7508 | push dword ptr [ebp + 8] $sequence_9 = { 8b45f8 8b08 8b9180000000 50 } // n = 4, score = 800 // 8b45f8 | mov eax, dword ptr [ebp - 8] // 8b08 | mov ecx, dword ptr [eax] // 8b9180000000 | mov edx, dword ptr [ecx + 0x80] // 50 | push eax condition: 7 of them and filesize < 57344 }
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