rule win_bistromath_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-05-04"
        version = "1"
        description = "Detects win.bistromath."
        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.bistromath"
        malpedia_rule_date = "20260422"
        malpedia_hash = "a182e35da64e6d71cb55f125c4d4225196523f14"
        malpedia_version = "20260504"
        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 = { eb4c 8b4de8 33c0 8bd7 66894314 e8???????? 85c0 }
            // n = 7, score = 400
            //   eb4c                 | jmp                 0x4e
            //   8b4de8               | mov                 ecx, dword ptr [ebp - 0x18]
            //   33c0                 | xor                 eax, eax
            //   8bd7                 | mov                 edx, edi
            //   66894314             | mov                 word ptr [ebx + 0x14], ax
            //   e8????????           |                     
            //   85c0                 | test                eax, eax

        $sequence_1 = { e8???????? 2500030000 c3 8bff 55 8bec 668b4d0e }
            // n = 7, score = 400
            //   e8????????           |                     
            //   2500030000           | and                 eax, 0x300
            //   c3                   | ret                 
            //   8bff                 | mov                 edi, edi
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   668b4d0e             | mov                 cx, word ptr [ebp + 0xe]

        $sequence_2 = { eb03 8b5dc4 8b5508 83c730 3b7de4 0f8200ffffff 33ff }
            // n = 7, score = 400
            //   eb03                 | jmp                 5
            //   8b5dc4               | mov                 ebx, dword ptr [ebp - 0x3c]
            //   8b5508               | mov                 edx, dword ptr [ebp + 8]
            //   83c730               | add                 edi, 0x30
            //   3b7de4               | cmp                 edi, dword ptr [ebp - 0x1c]
            //   0f8200ffffff         | jb                  0xffffff06
            //   33ff                 | xor                 edi, edi

        $sequence_3 = { e8???????? 3b450c 7430 8bcf e8???????? 8903 85c0 }
            // n = 7, score = 400
            //   e8????????           |                     
            //   3b450c               | cmp                 eax, dword ptr [ebp + 0xc]
            //   7430                 | je                  0x32
            //   8bcf                 | mov                 ecx, edi
            //   e8????????           |                     
            //   8903                 | mov                 dword ptr [ebx], eax
            //   85c0                 | test                eax, eax

        $sequence_4 = { eb16 84db 7406 02c3 3c62 75db 8b4d0c }
            // n = 7, score = 400
            //   eb16                 | jmp                 0x18
            //   84db                 | test                bl, bl
            //   7406                 | je                  8
            //   02c3                 | add                 al, bl
            //   3c62                 | cmp                 al, 0x62
            //   75db                 | jne                 0xffffffdd
            //   8b4d0c               | mov                 ecx, dword ptr [ebp + 0xc]

        $sequence_5 = { ffd0 83c414 85c0 0f850f010000 8b4df4 8b5340 83c104 }
            // n = 7, score = 400
            //   ffd0                 | call                eax
            //   83c414               | add                 esp, 0x14
            //   85c0                 | test                eax, eax
            //   0f850f010000         | jne                 0x115
            //   8b4df4               | mov                 ecx, dword ptr [ebp - 0xc]
            //   8b5340               | mov                 edx, dword ptr [ebx + 0x40]
            //   83c104               | add                 ecx, 4

        $sequence_6 = { eb0b 85f6 0f85c9000000 8b4508 8d34dd01000000 8bc8 8bd6 }
            // n = 7, score = 400
            //   eb0b                 | jmp                 0xd
            //   85f6                 | test                esi, esi
            //   0f85c9000000         | jne                 0xcf
            //   8b4508               | mov                 eax, dword ptr [ebp + 8]
            //   8d34dd01000000       | lea                 esi, [ebx*8 + 1]
            //   8bc8                 | mov                 ecx, eax
            //   8bd6                 | mov                 edx, esi

        $sequence_7 = { ff742424 e8???????? 83c410 8b442418 c6401101 8b442440 ff4018 }
            // n = 7, score = 400
            //   ff742424             | push                dword ptr [esp + 0x24]
            //   e8????????           |                     
            //   83c410               | add                 esp, 0x10
            //   8b442418             | mov                 eax, dword ptr [esp + 0x18]
            //   c6401101             | mov                 byte ptr [eax + 0x11], 1
            //   8b442440             | mov                 eax, dword ptr [esp + 0x40]
            //   ff4018               | inc                 dword ptr [eax + 0x18]

        $sequence_8 = { eb09 ff7708 50 68???????? 50 53 e8???????? }
            // n = 7, score = 400
            //   eb09                 | jmp                 0xb
            //   ff7708               | push                dword ptr [edi + 8]
            //   50                   | push                eax
            //   68????????           |                     
            //   50                   | push                eax
            //   53                   | push                ebx
            //   e8????????           |                     

        $sequence_9 = { 8bec 83ec20 803900 7506 33c0 8be5 5d }
            // n = 7, score = 400
            //   8bec                 | mov                 ebp, esp
            //   83ec20               | sub                 esp, 0x20
            //   803900               | cmp                 byte ptr [ecx], 0
            //   7506                 | jne                 8
            //   33c0                 | xor                 eax, eax
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp

    condition:
        7 of them and filesize < 33816576
}