Actor(s): Lazarus Group
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rule win_sierras_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2021-10-07" version = "1" description = "Detects win.sierras." 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.sierras" malpedia_rule_date = "20211007" malpedia_hash = "e5b790e0f888f252d49063a1251ca60ec2832535" malpedia_version = "20211008" 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 = { c705????????07000000 8935???????? 8935???????? 8935???????? 8935???????? ff15???????? 3bc6 } // n = 7, score = 400 // c705????????07000000 | // 8935???????? | // 8935???????? | // 8935???????? | // 8935???????? | // ff15???????? | // 3bc6 | cmp eax, esi $sequence_1 = { c7060c000000 ebdf 83ff10 7324 837df800 0f84d80f0000 } // n = 6, score = 200 // c7060c000000 | mov dword ptr [esi], 0xc // ebdf | jmp 0xffffffe1 // 83ff10 | cmp edi, 0x10 // 7324 | jae 0x26 // 837df800 | cmp dword ptr [ebp - 8], 0 // 0f84d80f0000 | je 0xfde $sequence_2 = { d1e2 f2ae f7d1 8db220e24000 2bf9 8bc1 89742428 } // n = 7, score = 200 // d1e2 | shl edx, 1 // f2ae | repne scasb al, byte ptr es:[edi] // f7d1 | not ecx // 8db220e24000 | lea esi, dword ptr [edx + 0x40e220] // 2bf9 | sub edi, ecx // 8bc1 | mov eax, ecx // 89742428 | mov dword ptr [esp + 0x28], esi $sequence_3 = { ffd7 8b4c2438 6a00 6a00 51 } // n = 5, score = 200 // ffd7 | call edi // 8b4c2438 | mov ecx, dword ptr [esp + 0x38] // 6a00 | push 0 // 6a00 | push 0 // 51 | push ecx $sequence_4 = { f3ab 66ab aa ff15???????? 50 ff15???????? } // n = 6, score = 200 // f3ab | rep stosd dword ptr es:[edi], eax // 66ab | stosw word ptr es:[edi], ax // aa | stosb byte ptr es:[edi], al // ff15???????? | // 50 | push eax // ff15???????? | $sequence_5 = { 52 e8???????? 8b3d???????? 83c404 8bd8 } // n = 5, score = 200 // 52 | push edx // e8???????? | // 8b3d???????? | // 83c404 | add esp, 4 // 8bd8 | mov ebx, eax $sequence_6 = { 8bc3 837d0800 50 8b450c 7511 8b4dec 03c7 } // n = 7, score = 200 // 8bc3 | mov eax, ebx // 837d0800 | cmp dword ptr [ebp + 8], 0 // 50 | push eax // 8b450c | mov eax, dword ptr [ebp + 0xc] // 7511 | jne 0x13 // 8b4dec | mov ecx, dword ptr [ebp - 0x14] // 03c7 | add eax, edi $sequence_7 = { eb0f 8b4dec 03c7 50 8d45e0 50 } // n = 6, score = 200 // eb0f | jmp 0x11 // 8b4dec | mov ecx, dword ptr [ebp - 0x14] // 03c7 | add eax, edi // 50 | push eax // 8d45e0 | lea eax, dword ptr [ebp - 0x20] // 50 | push eax $sequence_8 = { 0f8cc0000000 837d0801 7e58 837d0803 0f8fb0000000 397d10 897df0 } // n = 7, score = 200 // 0f8cc0000000 | jl 0xc6 // 837d0801 | cmp dword ptr [ebp + 8], 1 // 7e58 | jle 0x5a // 837d0803 | cmp dword ptr [ebp + 8], 3 // 0f8fb0000000 | jg 0xb6 // 397d10 | cmp dword ptr [ebp + 0x10], edi // 897df0 | mov dword ptr [ebp - 0x10], edi $sequence_9 = { 0f84d80f0000 8b4dfc ff4df8 0fb611 8bcf d3e2 03da } // n = 7, score = 200 // 0f84d80f0000 | je 0xfde // 8b4dfc | mov ecx, dword ptr [ebp - 4] // ff4df8 | dec dword ptr [ebp - 8] // 0fb611 | movzx edx, byte ptr [ecx] // 8bcf | mov ecx, edi // d3e2 | shl edx, cl // 03da | add ebx, edx $sequence_10 = { 3bc1 75f3 eb43 50 50 } // n = 5, score = 200 // 3bc1 | cmp eax, ecx // 75f3 | jne 0xfffffff5 // eb43 | jmp 0x45 // 50 | push eax // 50 | push eax $sequence_11 = { 017514 03fb 3b7d10 72b0 8b5df0 } // n = 5, score = 200 // 017514 | add dword ptr [ebp + 0x14], esi // 03fb | add edi, ebx // 3b7d10 | cmp edi, dword ptr [ebp + 0x10] // 72b0 | jb 0xffffffb2 // 8b5df0 | mov ebx, dword ptr [ebp - 0x10] $sequence_12 = { 56 8bf1 57 68???????? 8d8608020000 } // n = 5, score = 200 // 56 | push esi // 8bf1 | mov esi, ecx // 57 | push edi // 68???????? | // 8d8608020000 | lea eax, dword ptr [esi + 0x208] $sequence_13 = { 8b8424a4220000 8b8c24a0220000 8d942480000000 52 8b9424a0220000 50 } // n = 6, score = 200 // 8b8424a4220000 | mov eax, dword ptr [esp + 0x22a4] // 8b8c24a0220000 | mov ecx, dword ptr [esp + 0x22a0] // 8d942480000000 | lea edx, dword ptr [esp + 0x80] // 52 | push edx // 8b9424a0220000 | mov edx, dword ptr [esp + 0x22a0] // 50 | push eax $sequence_14 = { c3 56 8bf1 e8???????? 8b860c010000 5e c3 } // n = 7, score = 200 // c3 | ret // 56 | push esi // 8bf1 | mov esi, ecx // e8???????? | // 8b860c010000 | mov eax, dword ptr [esi + 0x10c] // 5e | pop esi // c3 | ret condition: 7 of them and filesize < 131072 }
import "pe" rule win_sierras_w0 { meta: copyright = "2015 Novetta Solutions" author = "Novetta Threat Research & Interdiction Group - trig@novetta.com" info = "charlie component" hash = "f4750e1d82b08318bdc1eb6d3399dee52750250f7959a5e4f83245449f399698" source = "https://github.com/mattulm/sfiles_yara/blob/master/malware/SierraCharlie.yar" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.sierras" malpedia_version = "20170517" malpedia_license = "CC BY-NC-SA 4.0" malpedia_sharing = "TLP:WHITE" strings: /* 8B 0D 50 A7 56 00 mov ecx, DnsFree 81 F6 8C 3F 7C 5E xor esi, 5E7C3F8Ch 6A 01 push 1 ; _DWORD 50 push eax ; _DWORD 85 C9 test ecx, ecx 74 3A jz short loc_40580B FF D1 call ecx ; DnsFree */ $dnsResolve = { 8B 0D 50 A7 56 00 81 F6 8C 3F 7C 5E 6A 01 50 85 C9 74 3A FF D1 } $file1 = "wmplog21t.sqm" $file2 = "wmplog15r.sqm" $file3 = "wmplog09c.sqm" condition: $dnsResolve in ((pe.sections[pe.section_index(".text")].raw_data_offset)..(pe.sections[pe.section_index(".text")].raw_data_offset + pe.sections[pe.section_index(".text")].raw_data_size)) or 2 of ($file*) }
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