Ransomware.
rule win_smrss32_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2020-10-14" version = "1" description = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.5.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.smrss32" malpedia_rule_date = "20201014" malpedia_hash = "a7e3bd57eaf12bf3ea29a863c041091ba3af9ac9" malpedia_version = "20201014" 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 = { e8???????? 89442434 e9???????? e8???????? e8???????? 38d8 } // n = 6, score = 100 // e8???????? | // 89442434 | mov dword ptr [esp + 0x34], eax // e9???????? | // e8???????? | // e8???????? | // 38d8 | cmp al, bl $sequence_1 = { e8???????? 89b585680000 6884ef314f e8???????? 8d442428 8974244c 96 } // n = 7, score = 100 // e8???????? | // 89b585680000 | mov dword ptr [ebp + 0x6885], esi // 6884ef314f | push 0x4f31ef84 // e8???????? | // 8d442428 | lea eax, [esp + 0x28] // 8974244c | mov dword ptr [esp + 0x4c], esi // 96 | xchg eax, esi $sequence_2 = { 56 648b1530000000 85d2 782c 40 4e b46a } // n = 7, score = 100 // 56 | push esi // 648b1530000000 | mov edx, dword ptr fs:[0x30] // 85d2 | test edx, edx // 782c | js 0x2e // 40 | inc eax // 4e | dec esi // b46a | mov ah, 0x6a $sequence_3 = { 8f461c c746140c000000 8d8563ffffff 50 897618 806e02fc 6a04 } // n = 7, score = 100 // 8f461c | pop dword ptr [esi + 0x1c] // c746140c000000 | mov dword ptr [esi + 0x14], 0xc // 8d8563ffffff | lea eax, [ebp - 0x9d] // 50 | push eax // 897618 | mov dword ptr [esi + 0x18], esi // 806e02fc | sub byte ptr [esi + 2], 0xfc // 6a04 | push 4 $sequence_4 = { ffd7 ff542450 fe0c24 75f2 87d7 f6d6 58 } // n = 7, score = 100 // ffd7 | call edi // ff542450 | call dword ptr [esp + 0x50] // fe0c24 | dec byte ptr [esp] // 75f2 | jne 0xfffffff4 // 87d7 | xchg edi, edx // f6d6 | not dh // 58 | pop eax $sequence_5 = { 8bfe 6a04 59 58 ab 48 } // n = 6, score = 100 // 8bfe | mov edi, esi // 6a04 | push 4 // 59 | pop ecx // 58 | pop eax // ab | stosd dword ptr es:[edi], eax // 48 | dec eax $sequence_6 = { e8???????? 89442434 e9???????? e8???????? e8???????? 38d8 7509 } // n = 7, score = 100 // e8???????? | // 89442434 | mov dword ptr [esp + 0x34], eax // e9???????? | // e8???????? | // e8???????? | // 38d8 | cmp al, bl // 7509 | jne 0xb $sequence_7 = { 49 68d67d53f3 e8???????? 89742444 } // n = 4, score = 100 // 49 | dec ecx // 68d67d53f3 | push 0xf3537dd6 // e8???????? | // 89742444 | mov dword ptr [esp + 0x44], esi $sequence_8 = { ff857d680000 ff542458 54 ff54245c } // n = 4, score = 100 // ff857d680000 | inc dword ptr [ebp + 0x687d] // ff542458 | call dword ptr [esp + 0x58] // 54 | push esp // ff54245c | call dword ptr [esp + 0x5c] $sequence_9 = { 47 96 3400 e8???????? } // n = 4, score = 100 // 47 | inc edi // 96 | xchg eax, esi // 3400 | xor al, 0 // e8???????? | condition: 7 of them and filesize < 427008 }
If your designated proposal does not fit in any other category, feel free to write a free-text in the comment field below. Changes regarding references should be proposed on the Malpedia library page.
Your suggestion will be reviewed before being published. Thank you for contributing!
YYYY-MM-DD
YYYY-MM
YYYY