According to Proofpoint, Overlord is an open-source RAT written in Go.
rule win_overlord_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2026-09-17" version = "1" description = "Detects win.overlord." 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.overlord" malpedia_rule_date = "20260916" malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6" malpedia_version = "20260917" 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 = { e9???????? 31ff e8???????? 8b5c2474 e9???????? 894500 400fb6ff } // n = 7, score = 100 // e9???????? | // 31ff | dec esp // e8???????? | // 8b5c2474 | mov edx, dword ptr [esp + 0x48] // e9???????? | // 894500 | mov edi, eax // 400fb6ff | inc ebx $sequence_1 = { ffd1 b932000000 4889c7 4889de 31c0 488d1d6fc84e00 0f1f00 } // n = 7, score = 100 // ffd1 | dec eax // b932000000 | mov edx, dword ptr [eax] // 4889c7 | nop word ptr [eax + eax] // 4889de | dec eax // 31c0 | test edx, edx // 488d1d6fc84e00 | je 0xb3e // 0f1f00 | dec edx $sequence_2 = { 75e3 4889442418 488d052f834200 e8???????? 4889c1 488b442418 6690 } // n = 7, score = 100 // 75e3 | add edi, 0x10 // 4889442418 | dec esp // 488d052f834200 | mov eax, dword ptr [esp + 0x38] // e8???????? | // 4889c1 | dec ecx // 488b442418 | dec eax // 6690 | dec eax $sequence_3 = { e8???????? 488d1571bf2c00 483910 7506 488b7008 eb06 31f6 } // n = 7, score = 100 // e8???????? | // 488d1571bf2c00 | test al, al // 483910 | dec eax // 7506 | mov dword ptr [esp + 0x138], 0 // 488b7008 | dec eax // eb06 | mov edx, dword ptr [ebx + 0x20] // 31f6 | dec eax $sequence_4 = { e8???????? eb05 83f902 751c 90 b9ffffffff 488d159113a800 } // n = 7, score = 100 // e8???????? | // eb05 | dec eax // 83f902 | lea eax, [eax + eax*2] // 751c | dec eax // 90 | shl eax, 0xa // b9ffffffff | dec eax // 488d159113a800 | mov dword ptr [esp + 0x50], eax $sequence_5 = { 8b8c24b0000000 488b9180010000 e8???????? 488bb42488000000 498933 49894308 49895310 } // n = 7, score = 100 // 8b8c24b0000000 | dec eax // 488b9180010000 | mov ecx, dword ptr [esp + 0x110] // e8???????? | // 488bb42488000000 | dec eax // 498933 | mov edx, dword ptr [ecx + 0x60] // 49894308 | dec eax // 49895310 | lea eax, [0xa9ac7c] $sequence_6 = { f30f6f51f0 f30f6f71f0 f3450f6f40c0 66410fdbcd 66410fdbd5 66440f6f3424 660f67d9 } // n = 7, score = 100 // f30f6f51f0 | arpl word ptr [ebp + 0x5f88], ax // f30f6f71f0 | dec eax // f3450f6f40c0 | mov ecx, dword ptr [eax + 0x30b0] // 66410fdbcd | dec ebp // 66410fdbd5 | add eax, eax // 66440f6f3424 | test esi, esi // 660f67d9 | jne 0x388 $sequence_7 = { e8???????? 4c8b9c2460010000 4d8b4b18 4c8b9c2400010000 4d0fafcb 4c01d9 4d01dc } // n = 7, score = 100 // e8???????? | // 4c8b9c2460010000 | dec ecx // 4d8b4b18 | cmp dword ptr [esp + 0x20], 0 // 4c8b9c2400010000 | jne 0x38b // 4d0fafcb | dec esp // 4c01d9 | lea esi, [0x26d8cd2] // 4d01dc | dec esp $sequence_8 = { f30f2cd0 90 eb62 488d3537152a00 4839f2 754e 418b10 } // n = 7, score = 100 // f30f2cd0 | xor ebp, ebp // 90 | inc sp // eb62 | mov dword ptr [eax], esp // 488d3537152a00 | dec ecx // 4839f2 | mov ebp, ebx // 754e | mov ebx, dword ptr [esp + 0x98] // 418b10 | cmp dword ptr [esp + 0x80], 3 $sequence_9 = { ffd6 488b8ba8020000 ffd6 488b8b50020000 ffd6 488d4378 48394370 } // n = 7, score = 100 // ffd6 | test edi, edi // 488b8ba8020000 | je 0x10e4 // ffd6 | dec eax // 488b8b50020000 | mov eax, dword ptr [edi + 0x30] // ffd6 | dec eax // 488d4378 | test eax, eax // 48394370 | je 0x10d8 condition: 7 of them and filesize < 91286528 }
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