Actor(s): Turla
There is no description at this point.
rule win_outlook_backdoor_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.outlook_backdoor." 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.outlook_backdoor" malpedia_rule_date = "20231130" malpedia_hash = "fc8a0e9f343f6d6ded9e7df1a64dac0cc68d7351" malpedia_version = "20230808" 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 = { ff753c 53 68e9fd0000 ffd6 8d4d00 894568 e8???????? } // n = 7, score = 600 // ff753c | push dword ptr [ebp + 0x3c] // 53 | push ebx // 68e9fd0000 | push 0xfde9 // ffd6 | call esi // 8d4d00 | lea ecx, [ebp] // 894568 | mov dword ptr [ebp + 0x68], eax // e8???????? | $sequence_1 = { ff10 8b4c2408 ff74240c 8d04c8 8b4804 85c9 740b } // n = 7, score = 600 // ff10 | call dword ptr [eax] // 8b4c2408 | mov ecx, dword ptr [esp + 8] // ff74240c | push dword ptr [esp + 0xc] // 8d04c8 | lea eax, [eax + ecx*8] // 8b4804 | mov ecx, dword ptr [eax + 4] // 85c9 | test ecx, ecx // 740b | je 0xd $sequence_2 = { c9 c20800 56 8bf7 e8???????? 8d771c e8???????? } // n = 7, score = 600 // c9 | leave // c20800 | ret 8 // 56 | push esi // 8bf7 | mov esi, edi // e8???????? | // 8d771c | lea esi, [edi + 0x1c] // e8???????? | $sequence_3 = { c745e01f000130 895d0c ff15???????? 8b450c 8945f0 895dfc 33c9 } // n = 7, score = 600 // c745e01f000130 | mov dword ptr [ebp - 0x20], 0x3001001f // 895d0c | mov dword ptr [ebp + 0xc], ebx // ff15???????? | // 8b450c | mov eax, dword ptr [ebp + 0xc] // 8945f0 | mov dword ptr [ebp - 0x10], eax // 895dfc | mov dword ptr [ebp - 4], ebx // 33c9 | xor ecx, ecx $sequence_4 = { 6898000000 e8???????? 59 8945ec c645fc01 } // n = 5, score = 600 // 6898000000 | push 0x98 // e8???????? | // 59 | pop ecx // 8945ec | mov dword ptr [ebp - 0x14], eax // c645fc01 | mov byte ptr [ebp - 4], 1 $sequence_5 = { f6455404 740e 836554fb 57 56 8d4dbc e8???????? } // n = 7, score = 600 // f6455404 | test byte ptr [ebp + 0x54], 4 // 740e | je 0x10 // 836554fb | and dword ptr [ebp + 0x54], 0xfffffffb // 57 | push edi // 56 | push esi // 8d4dbc | lea ecx, [ebp - 0x44] // e8???????? | $sequence_6 = { c3 57 6a2c e8???????? 8bf8 59 85ff } // n = 7, score = 600 // c3 | ret // 57 | push edi // 6a2c | push 0x2c // e8???????? | // 8bf8 | mov edi, eax // 59 | pop ecx // 85ff | test edi, edi $sequence_7 = { 5f 5e 8d4302 5b c3 53 8bd9 } // n = 7, score = 600 // 5f | pop edi // 5e | pop esi // 8d4302 | lea eax, [ebx + 2] // 5b | pop ebx // c3 | ret // 53 | push ebx // 8bd9 | mov ebx, ecx $sequence_8 = { 50 e8???????? 834d1004 f6451002 740f 836510fd } // n = 6, score = 600 // 50 | push eax // e8???????? | // 834d1004 | or dword ptr [ebp + 0x10], 4 // f6451002 | test byte ptr [ebp + 0x10], 2 // 740f | je 0x11 // 836510fd | and dword ptr [ebp + 0x10], 0xfffffffd $sequence_9 = { e8???????? 83ec38 56 57 8bf1 8b4604 33ff } // n = 7, score = 600 // e8???????? | // 83ec38 | sub esp, 0x38 // 56 | push esi // 57 | push edi // 8bf1 | mov esi, ecx // 8b4604 | mov eax, dword ptr [esi + 4] // 33ff | xor edi, edi condition: 7 of them and filesize < 2912256 }
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