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 = "2023-01-25" 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 = "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 = { 33f6 8d6e20 8bcd e8???????? } // n = 4, score = 1300 // 33f6 | mov eax, esi // 8d6e20 | xor edx, edx // 8bcd | inc ecx // e8???????? | $sequence_1 = { 410fbe00 49ffc0 d3ca 03d0 4183ef01 } // n = 5, score = 1300 // 410fbe00 | inc ecx // 49ffc0 | movsx eax, byte ptr [eax] // d3ca | dec ecx // 03d0 | inc eax // 4183ef01 | ror edx, cl $sequence_2 = { 458bc6 33d2 488bc8 e8???????? 4533c9 4533c0 } // n = 6, score = 1300 // 458bc6 | mov eax, eax // 33d2 | imul ecx // 488bc8 | add edx, ecx // e8???????? | // 4533c9 | sar edx, 0xb // 4533c0 | mov eax, edx $sequence_3 = { ff15???????? 448bf0 4533c9 4533c0 } // n = 4, score = 1300 // ff15???????? | // 448bf0 | inc ecx // 4533c9 | movsx eax, byte ptr [eax] // 4533c0 | dec ecx $sequence_4 = { 4c8bc6 33d2 410fbe00 49ffc0 } // n = 4, score = 1300 // 4c8bc6 | inc ebp // 33d2 | mov eax, esi // 410fbe00 | xor edx, edx // 49ffc0 | dec eax $sequence_5 = { c1fa0b 8bc2 c1e81f 03d0 69c2890e0000 } // n = 5, score = 1300 // c1fa0b | add edx, eax // 8bc2 | inc ecx // c1e81f | sub edi, 1 // 03d0 | inc ebp // 69c2890e0000 | mov eax, esi $sequence_6 = { 41b88d56e68c 418bc0 f7e9 03d1 c1fa0b 8bc2 } // n = 6, score = 1300 // 41b88d56e68c | add edx, eax // 418bc0 | inc ecx // f7e9 | sub edi, 1 // 03d1 | inc ecx // c1fa0b | mov eax, 0x8ce6568d // 8bc2 | inc ecx $sequence_7 = { 458d7ee0 418bd7 ff15???????? 4821742420 } // n = 4, score = 1300 // 458d7ee0 | inc ecx // 418bd7 | sub edi, 1 // ff15???????? | // 4821742420 | dec esp $sequence_8 = { eb17 81fa00010000 7313 8a87f4814100 08441619 } // n = 5, 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 $sequence_9 = { eb7c c745e0205b4100 ebbb d9e8 8b4510 } // n = 5, score = 200 // eb7c | jmp 0x7e // c745e0205b4100 | mov dword ptr [ebp - 0x20], 0x415b20 // ebbb | jmp 0xffffffbd // d9e8 | fld1 // 8b4510 | mov eax, dword ptr [ebp + 0x10] $sequence_10 = { c1e002 50 8b85b4f8ffff 0fb70485c4574100 8d0485c04e4100 50 } // n = 6, score = 200 // c1e002 | shl eax, 2 // 50 | push eax // 8b85b4f8ffff | mov eax, dword ptr [ebp - 0x74c] // 0fb70485c4574100 | movzx eax, word ptr [eax*4 + 0x4157c4] // 8d0485c04e4100 | lea eax, [eax*4 + 0x414ec0] // 50 | push eax $sequence_11 = { ff15???????? 85c0 7f32 68???????? } // n = 4, score = 200 // ff15???????? | // 85c0 | test eax, eax // 7f32 | jg 0x34 // 68???????? | $sequence_12 = { 8b0485808e4100 8b4de0 f644082801 7515 } // n = 4, score = 200 // 8b0485808e4100 | mov eax, dword ptr [eax*4 + 0x418e80] // 8b4de0 | mov ecx, dword ptr [ebp - 0x20] // f644082801 | test byte ptr [eax + ecx + 0x28], 1 // 7515 | jne 0x17 $sequence_13 = { 8934b8 8bc7 83e03f 6bc830 8b0495808e4100 8b440818 } // n = 6, score = 200 // 8934b8 | mov dword ptr [eax + edi*4], esi // 8bc7 | mov eax, edi // 83e03f | and eax, 0x3f // 6bc830 | imul ecx, eax, 0x30 // 8b0495808e4100 | mov eax, dword ptr [edx*4 + 0x418e80] // 8b440818 | mov eax, dword ptr [eax + ecx + 0x18] $sequence_14 = { 0f82eefeffff eb29 8b55d4 8a07 8b0c95808e4100 8844192e 8b0495808e4100 } // n = 7, score = 200 // 0f82eefeffff | jb 0xfffffef4 // eb29 | jmp 0x2b // 8b55d4 | mov edx, dword ptr [ebp - 0x2c] // 8a07 | mov al, byte ptr [edi] // 8b0c95808e4100 | mov ecx, dword ptr [edx*4 + 0x418e80] // 8844192e | mov byte ptr [ecx + ebx + 0x2e], al // 8b0495808e4100 | mov eax, dword ptr [edx*4 + 0x418e80] $sequence_15 = { 8bde 895dd8 8365fc00 8b45e4 8b0485808e4100 8b4de0 } // n = 6, 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] 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