Information stealer.
rule win_ufrstealer_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2023-12-06" version = "1" description = "Detects win.ufrstealer." 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.ufrstealer" 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 = { 6a01 6a00 6a00 68???????? 6a00 68???????? ff15???????? } // n = 7, score = 200 // 6a01 | push 1 // 6a00 | push 0 // 6a00 | push 0 // 68???????? | // 6a00 | push 0 // 68???????? | // ff15???????? | $sequence_1 = { 0bc0 7529 8b43fc 03d8 8b03 83c304 83f8ff } // n = 7, score = 200 // 0bc0 | or eax, eax // 7529 | jne 0x2b // 8b43fc | mov eax, dword ptr [ebx - 4] // 03d8 | add ebx, eax // 8b03 | mov eax, dword ptr [ebx] // 83c304 | add ebx, 4 // 83f8ff | cmp eax, -1 $sequence_2 = { ffb5ecf3ffff ff15???????? 5b 5f 5e c9 } // n = 6, score = 200 // ffb5ecf3ffff | push dword ptr [ebp - 0xc14] // ff15???????? | // 5b | pop ebx // 5f | pop edi // 5e | pop esi // c9 | leave $sequence_3 = { 894df4 8b75f4 83ee01 c745f008000000 0fb64eff 0fb616 83f97f } // n = 7, score = 200 // 894df4 | mov dword ptr [ebp - 0xc], ecx // 8b75f4 | mov esi, dword ptr [ebp - 0xc] // 83ee01 | sub esi, 1 // c745f008000000 | mov dword ptr [ebp - 0x10], 8 // 0fb64eff | movzx ecx, byte ptr [esi - 1] // 0fb616 | movzx edx, byte ptr [esi] // 83f97f | cmp ecx, 0x7f $sequence_4 = { 03c1 80383a 7505 c60000 eb03 49 } // n = 6, score = 200 // 03c1 | add eax, ecx // 80383a | cmp byte ptr [eax], 0x3a // 7505 | jne 7 // c60000 | mov byte ptr [eax], 0 // eb03 | jmp 5 // 49 | dec ecx $sequence_5 = { ff35???????? ff15???????? 85c0 0f842debffff a3???????? 68???????? ff15???????? } // n = 7, score = 200 // ff35???????? | // ff15???????? | // 85c0 | test eax, eax // 0f842debffff | je 0xffffeb33 // a3???????? | // 68???????? | // ff15???????? | $sequence_6 = { 0f85c0000000 0fb60d???????? a1???????? 8808 8305????????01 894dfc bb???????? } // n = 7, score = 200 // 0f85c0000000 | jne 0xc6 // 0fb60d???????? | // a1???????? | // 8808 | mov byte ptr [eax], cl // 8305????????01 | // 894dfc | mov dword ptr [ebp - 4], ecx // bb???????? | $sequence_7 = { 8d45dc 6a04 50 e8???????? 8305????????04 e8???????? } // n = 6, score = 200 // 8d45dc | lea eax, [ebp - 0x24] // 6a04 | push 4 // 50 | push eax // e8???????? | // 8305????????04 | // e8???????? | $sequence_8 = { 50 68???????? 68???????? 6a00 ff15???????? 68???????? ff15???????? } // n = 7, score = 200 // 50 | push eax // 68???????? | // 68???????? | // 6a00 | push 0 // ff15???????? | // 68???????? | // ff15???????? | $sequence_9 = { c745d80e000000 33c0 8b75d8 8bc8 8db65c884200 } // n = 5, score = 200 // c745d80e000000 | mov dword ptr [ebp - 0x28], 0xe // 33c0 | xor eax, eax // 8b75d8 | mov esi, dword ptr [ebp - 0x28] // 8bc8 | mov ecx, eax // 8db65c884200 | lea esi, [esi + 0x42885c] condition: 7 of them and filesize < 770048 }
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