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 = "2023-12-06" version = "1" description = "Detects win.systembc." 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.systembc" 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 = { 8b8e88010000 8b968c010000 8bb690010000 8945e4 895df4 } // n = 5, score = 800 // 8b8e88010000 | mov ecx, dword ptr [esi + 0x188] // 8b968c010000 | mov edx, dword ptr [esi + 0x18c] // 8bb690010000 | mov esi, dword ptr [esi + 0x190] // 8945e4 | mov dword ptr [ebp - 0x1c], eax // 895df4 | mov dword ptr [ebp - 0xc], ebx $sequence_1 = { 52 6a00 6a00 6a00 ffb568f9ffff } // n = 5, score = 800 // 52 | push edx // 6a00 | push 0 // 6a00 | push 0 // 6a00 | push 0 // ffb568f9ffff | push dword ptr [ebp - 0x698] $sequence_2 = { 668b9554f9ffff 6a00 6a00 6a03 6a00 6a00 } // n = 6, score = 800 // 668b9554f9ffff | mov dx, word ptr [ebp - 0x6ac] // 6a00 | push 0 // 6a00 | push 0 // 6a03 | push 3 // 6a00 | push 0 // 6a00 | push 0 $sequence_3 = { 898568f9ffff c7856cf9ffff00040000 8d853cf9ffff 50 6a00 6a00 } // n = 6, score = 800 // 898568f9ffff | mov dword ptr [ebp - 0x698], eax // c7856cf9ffff00040000 | mov dword ptr [ebp - 0x694], 0x400 // 8d853cf9ffff | lea eax, [ebp - 0x6c4] // 50 | push eax // 6a00 | push 0 // 6a00 | push 0 $sequence_4 = { 81c200008000 81c200100000 81c200200000 6a00 52 } // n = 5, score = 800 // 81c200008000 | add edx, 0x800000 // 81c200100000 | add edx, 0x1000 // 81c200200000 | add edx, 0x2000 // 6a00 | push 0 // 52 | push edx $sequence_5 = { 8d851cf4ffff 50 6800010000 57 ffb530f4ffff } // n = 5, score = 800 // 8d851cf4ffff | lea eax, [ebp - 0xbe4] // 50 | push eax // 6800010000 | push 0x100 // 57 | push edi // ffb530f4ffff | push dword ptr [ebp - 0xbd0] $sequence_6 = { 50 e8???????? ffd0 8b85f4feffff } // n = 4, score = 800 // 50 | push eax // e8???????? | // ffd0 | call eax // 8b85f4feffff | mov eax, dword ptr [ebp - 0x10c] $sequence_7 = { 43 3b5dfc 7296 33c0 5e 5f } // n = 6, score = 800 // 43 | inc ebx // 3b5dfc | cmp ebx, dword ptr [ebp - 4] // 7296 | jb 0xffffff98 // 33c0 | xor eax, eax // 5e | pop esi // 5f | pop edi $sequence_8 = { 668b9554f9ffff 6a00 6a00 6a03 6a00 } // n = 5, score = 800 // 668b9554f9ffff | mov dx, word ptr [ebp - 0x6ac] // 6a00 | push 0 // 6a00 | push 0 // 6a03 | push 3 // 6a00 | push 0 $sequence_9 = { 57 56 8b7d10 33c0 } // n = 4, score = 800 // 57 | push edi // 56 | push esi // 8b7d10 | mov edi, dword ptr [ebp + 0x10] // 33c0 | xor eax, eax condition: 7 of them and filesize < 57344 }
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