Actor(s): Anunak, TA505
TinyMet is a meterpreter stager.
rule win_tinymet_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-01-25" version = "1" description = "Detects win.tinymet." 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.tinymet" malpedia_rule_date = "20230124" malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686" malpedia_version = "20230125" 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 = { 68???????? e9???????? ff15???????? 85c0 7407 } // n = 5, score = 100 // 68???????? | // e9???????? | // ff15???????? | // 85c0 | test eax, eax // 7407 | je 9 $sequence_1 = { 53 56 53 53 53 8d4de8 } // n = 6, score = 100 // 53 | push ebx // 56 | push esi // 53 | push ebx // 53 | push ebx // 53 | push ebx // 8d4de8 | lea ecx, [ebp - 0x18] $sequence_2 = { 0fbe00 83e830 743c 48 7435 48 741d } // n = 7, score = 100 // 0fbe00 | movsx eax, byte ptr [eax] // 83e830 | sub eax, 0x30 // 743c | je 0x3e // 48 | dec eax // 7435 | je 0x37 // 48 | dec eax // 741d | je 0x1f $sequence_3 = { ff750c 8b00 8b00 a3???????? e8???????? 59 50 } // n = 7, score = 100 // ff750c | push dword ptr [ebp + 0xc] // 8b00 | mov eax, dword ptr [eax] // 8b00 | mov eax, dword ptr [eax] // a3???????? | // e8???????? | // 59 | pop ecx // 50 | push eax $sequence_4 = { a1???????? 56 57 6a5c ff30 e8???????? 8bf0 } // n = 7, score = 100 // a1???????? | // 56 | push esi // 57 | push edi // 6a5c | push 0x5c // ff30 | push dword ptr [eax] // e8???????? | // 8bf0 | mov esi, eax $sequence_5 = { 56 ff15???????? 85c0 740a 68???????? e9???????? } // n = 6, score = 100 // 56 | push esi // ff15???????? | // 85c0 | test eax, eax // 740a | je 0xc // 68???????? | // e9???????? | $sequence_6 = { a3???????? 6a04 c600bf 8d45fc } // n = 4, score = 100 // a3???????? | // 6a04 | push 4 // c600bf | mov byte ptr [eax], 0xbf // 8d45fc | lea eax, [ebp - 4] $sequence_7 = { ff15???????? a3???????? 85c0 750a 68???????? } // n = 5, score = 100 // ff15???????? | // a3???????? | // 85c0 | test eax, eax // 750a | jne 0xc // 68???????? | condition: 7 of them and filesize < 57344 }
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