Actor(s): APT41
According to FireEye, CROSSWALK is a skeletal, modular backdoor capable of system survey and adding modules in response to C&C replies.
rule win_crosswalk_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.crosswalk." 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.crosswalk" 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 = { 33f6 8d6e20 8bcd e8???????? } // n = 4, score = 1300 // 33f6 | movsx eax, byte ptr [eax] // 8d6e20 | dec ecx // 8bcd | inc eax // e8???????? | $sequence_1 = { 458bc6 33d2 488bc8 e8???????? 4533c9 4533c0 } // n = 6, score = 1300 // 458bc6 | add edx, eax // 33d2 | imul eax, edx, 0xe89 // 488bc8 | inc ecx // e8???????? | // 4533c9 | mov eax, eax // 4533c0 | imul ecx $sequence_2 = { 4883ec28 4885c9 7402 ffd1 } // n = 4, score = 1300 // 4883ec28 | dec ecx // 4885c9 | inc eax // 7402 | ror edx, cl // ffd1 | inc ecx $sequence_3 = { 41b88d56e68c 418bc0 f7e9 03d1 c1fa0b 8bc2 } // n = 6, score = 1300 // 41b88d56e68c | dec ecx // 418bc0 | inc eax // f7e9 | ror edx, cl // 03d1 | add edx, eax // c1fa0b | inc ecx // 8bc2 | sub edi, 1 $sequence_4 = { 458d7ee0 418bd7 ff15???????? 4821742420 } // n = 4, score = 1300 // 458d7ee0 | xor edx, edx // 418bd7 | inc ecx // ff15???????? | // 4821742420 | movsx eax, byte ptr [eax] $sequence_5 = { c1fa0b 8bc2 c1e81f 03d0 69c2890e0000 } // n = 5, score = 1300 // c1fa0b | inc ecx // 8bc2 | mov eax, 0x8ce6568d // c1e81f | inc ecx // 03d0 | mov eax, eax // 69c2890e0000 | imul ecx $sequence_6 = { ff15???????? 448bf0 4533c9 4533c0 } // n = 4, score = 1300 // ff15???????? | // 448bf0 | inc esp // 4533c9 | mov esi, eax // 4533c0 | inc ebp $sequence_7 = { 33d2 410fbe00 49ffc0 d3ca 03d0 4183ef01 } // n = 6, score = 1300 // 33d2 | xor ecx, ecx // 410fbe00 | inc ebp // 49ffc0 | xor eax, eax // d3ca | xor edx, edx // 03d0 | inc ecx // 4183ef01 | movsx eax, byte ptr [eax] $sequence_8 = { 897de4 8365fc00 8b049d808e4100 8b4de0 } // n = 4, score = 200 // 897de4 | mov dword ptr [ebp - 0x1c], edi // 8365fc00 | and dword ptr [ebp - 4], 0 // 8b049d808e4100 | mov eax, dword ptr [ebx*4 + 0x418e80] // 8b4de0 | mov ecx, dword ptr [ebp - 0x20] $sequence_9 = { 8b0485808e4100 33db 8b7508 57 8b440818 8b4d10 8bf9 } // n = 7, score = 200 // 8b0485808e4100 | mov eax, dword ptr [eax*4 + 0x418e80] // 33db | xor ebx, ebx // 8b7508 | mov esi, dword ptr [ebp + 8] // 57 | push edi // 8b440818 | mov eax, dword ptr [eax + ecx + 0x18] // 8b4d10 | mov ecx, dword ptr [ebp + 0x10] // 8bf9 | mov edi, ecx $sequence_10 = { 8b45fc 817848f0844100 7409 ff7048 } // n = 4, score = 200 // 8b45fc | mov eax, dword ptr [ebp - 4] // 817848f0844100 | cmp dword ptr [eax + 0x48], 0x4184f0 // 7409 | je 0xb // ff7048 | push dword ptr [eax + 0x48] $sequence_11 = { 89861c020000 8b45e0 8d4e0c 6a06 8d90fc814100 } // n = 5, score = 200 // 89861c020000 | mov dword ptr [esi + 0x21c], eax // 8b45e0 | mov eax, dword ptr [ebp - 0x20] // 8d4e0c | lea ecx, [esi + 0xc] // 6a06 | push 6 // 8d90fc814100 | lea edx, [eax + 0x4181fc] $sequence_12 = { 83c404 8bd8 8d45fc 6a00 50 6a0c } // n = 6, score = 200 // 83c404 | add esp, 4 // 8bd8 | mov ebx, eax // 8d45fc | lea eax, [ebp - 4] // 6a00 | push 0 // 50 | push eax // 6a0c | push 0xc $sequence_13 = { 8bde 895dd8 8365fc00 8b45e4 8b0485808e4100 8b4de0 f644082801 } // n = 7, score = 200 // 8bde | mov ebx, esi // 895dd8 | mov dword ptr [ebp - 0x28], ebx // 8365fc00 | and dword ptr [ebp - 4], 0 // 8b45e4 | mov eax, dword ptr [ebp - 0x1c] // 8b0485808e4100 | mov eax, dword ptr [eax*4 + 0x418e80] // 8b4de0 | mov ecx, dword ptr [ebp - 0x20] // f644082801 | test byte ptr [eax + ecx + 0x28], 1 $sequence_14 = { 7810 3de4000000 7309 8b04c5502e4100 5d c3 33c0 } // n = 7, score = 200 // 7810 | js 0x12 // 3de4000000 | cmp eax, 0xe4 // 7309 | jae 0xb // 8b04c5502e4100 | mov eax, dword ptr [eax*8 + 0x412e50] // 5d | pop ebp // c3 | ret // 33c0 | xor eax, eax $sequence_15 = { eb17 81fa00010000 7313 8a87f4814100 08441619 42 } // n = 6, score = 200 // eb17 | jmp 0x19 // 81fa00010000 | cmp edx, 0x100 // 7313 | jae 0x15 // 8a87f4814100 | mov al, byte ptr [edi + 0x4181f4] // 08441619 | or byte ptr [esi + edx + 0x19], al // 42 | inc edx condition: 7 of them and filesize < 286720 }
If your designated proposal does not fit in any other category, feel free to write a free-text in the comment field below.
Please propose all changes regarding references on the Malpedia library page
Your suggestion will be reviewed before being published. Thank you for contributing!
YYYY-MM-DD
YYYY-MM
YYYY