This malware looks similar to WastedLocker, but the ransomware component is missing.
rule win_wastedloader_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-07-11" version = "1" description = "Detects win.wastedloader." 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.wastedloader" malpedia_rule_date = "20230705" malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41" malpedia_version = "20230715" 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 = { d1fe bb3c7bfba0 e106 85a7f7c88baa } // n = 4, score = 100 // d1fe | sar esi, 1 // bb3c7bfba0 | mov ebx, 0xa0fb7b3c // e106 | loope 8 // 85a7f7c88baa | test dword ptr [edi - 0x55743709], esp $sequence_1 = { d2eb 7ba5 01acff3d3bfc6d e78b ec f6d8 } // n = 6, score = 100 // d2eb | shr bl, cl // 7ba5 | jnp 0xffffffa7 // 01acff3d3bfc6d | add dword ptr [edi + edi*8 + 0x6dfc3b3d], ebp // e78b | out 0x8b, eax // ec | in al, dx // f6d8 | neg al $sequence_2 = { d193e13e7876 02dd ae 687b90c2e9 } // n = 4, score = 100 // d193e13e7876 | rcl dword ptr [ebx + 0x76783ee1], 1 // 02dd | add bl, ch // ae | scasb al, byte ptr es:[edi] // 687b90c2e9 | push 0xe9c2907b $sequence_3 = { af f6ff 8bef 69f2c46ff7ff } // n = 4, score = 100 // af | scasd eax, dword ptr es:[edi] // f6ff | idiv bh // 8bef | mov ebp, edi // 69f2c46ff7ff | imul esi, edx, 0xfff76fc4 $sequence_4 = { 0fb75114 83ea54 8b45f8 66895014 } // n = 4, score = 100 // 0fb75114 | movzx edx, word ptr [ecx + 0x14] // 83ea54 | sub edx, 0x54 // 8b45f8 | mov eax, dword ptr [ebp - 8] // 66895014 | mov word ptr [eax + 0x14], dx $sequence_5 = { 44 40 0433 381b } // n = 4, score = 100 // 44 | inc esp // 40 | inc eax // 0433 | add al, 0x33 // 381b | cmp byte ptr [ebx], bl $sequence_6 = { 8b55f8 66894a10 8b45f8 0fb74810 83e954 } // n = 5, score = 100 // 8b55f8 | mov edx, dword ptr [ebp - 8] // 66894a10 | mov word ptr [edx + 0x10], cx // 8b45f8 | mov eax, dword ptr [ebp - 8] // 0fb74810 | movzx ecx, word ptr [eax + 0x10] // 83e954 | sub ecx, 0x54 $sequence_7 = { 66894118 8b55f8 0fb74218 83e854 8b4df8 66894118 ba8d000000 } // n = 7, score = 100 // 66894118 | mov word ptr [ecx + 0x18], ax // 8b55f8 | mov edx, dword ptr [ebp - 8] // 0fb74218 | movzx eax, word ptr [edx + 0x18] // 83e854 | sub eax, 0x54 // 8b4df8 | mov ecx, dword ptr [ebp - 8] // 66894118 | mov word ptr [ecx + 0x18], ax // ba8d000000 | mov edx, 0x8d $sequence_8 = { 2cbe 832061 5b 5b } // n = 4, score = 100 // 2cbe | sub al, 0xbe // 832061 | and dword ptr [eax], 0x61 // 5b | pop ebx // 5b | pop ebx $sequence_9 = { 60 87cf 009c6ade5a5d02 46 89547ffe } // n = 5, score = 100 // 60 | pushal // 87cf | xchg edi, ecx // 009c6ade5a5d02 | add byte ptr [edx + ebp*2 + 0x25d5ade], bl // 46 | inc esi // 89547ffe | mov dword ptr [edi + edi*2 - 2], edx condition: 7 of them and filesize < 2677760 }
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