rule win_formbook_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.formbook."
        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.formbook"
        malpedia_rule_date = "20230705"
        malpedia_hash = "42d0574f4405bd7d2b154d321d345acb18834a41"
        malpedia_version = "20230715"
        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 = { 5e 8be5 5d c3 3c69 7544 8b7d18 }
            // n = 7, score = 2200
            //   5e                   | pop                 esi
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   3c69                 | cmp                 al, 0x69
            //   7544                 | jne                 0x46
            //   8b7d18               | mov                 edi, dword ptr [ebp + 0x18]

        $sequence_1 = { 52 50 bb01000000 e8???????? 83c40c 8b8ef4020000 51 }
            // n = 7, score = 2200
            //   52                   | push                edx
            //   50                   | push                eax
            //   bb01000000           | mov                 ebx, 1
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   8b8ef4020000         | mov                 ecx, dword ptr [esi + 0x2f4]
            //   51                   | push                ecx

        $sequence_2 = { b801000000 5d c3 55 8bec 81ec08020000 56 }
            // n = 7, score = 2200
            //   b801000000           | mov                 eax, 1
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   81ec08020000         | sub                 esp, 0x208
            //   56                   | push                esi

        $sequence_3 = { 8b550c 8b420c eb0b 83f864 750f 8b550c 8b421c }
            // n = 7, score = 2200
            //   8b550c               | mov                 edx, dword ptr [ebp + 0xc]
            //   8b420c               | mov                 eax, dword ptr [edx + 0xc]
            //   eb0b                 | jmp                 0xd
            //   83f864               | cmp                 eax, 0x64
            //   750f                 | jne                 0x11
            //   8b550c               | mov                 edx, dword ptr [ebp + 0xc]
            //   8b421c               | mov                 eax, dword ptr [edx + 0x1c]

        $sequence_4 = { 52 50 e8???????? ff07 83c40c 830602 5f }
            // n = 7, score = 2200
            //   52                   | push                edx
            //   50                   | push                eax
            //   e8????????           |                     
            //   ff07                 | inc                 dword ptr [edi]
            //   83c40c               | add                 esp, 0xc
            //   830602               | add                 dword ptr [esi], 2
            //   5f                   | pop                 edi

        $sequence_5 = { 56 e8???????? 83c438 85c0 7506 5e 5b }
            // n = 7, score = 2200
            //   56                   | push                esi
            //   e8????????           |                     
            //   83c438               | add                 esp, 0x38
            //   85c0                 | test                eax, eax
            //   7506                 | jne                 8
            //   5e                   | pop                 esi
            //   5b                   | pop                 ebx

        $sequence_6 = { 8a0439 03cf 8845f4 8d50c0 80fa1f 7718 6a01 }
            // n = 7, score = 2200
            //   8a0439               | mov                 al, byte ptr [ecx + edi]
            //   03cf                 | add                 ecx, edi
            //   8845f4               | mov                 byte ptr [ebp - 0xc], al
            //   8d50c0               | lea                 edx, [eax - 0x40]
            //   80fa1f               | cmp                 dl, 0x1f
            //   7718                 | ja                  0x1a
            //   6a01                 | push                1

        $sequence_7 = { 50 e8???????? 6a14 8d4d98 51 56 33db }
            // n = 7, score = 2200
            //   50                   | push                eax
            //   e8????????           |                     
            //   6a14                 | push                0x14
            //   8d4d98               | lea                 ecx, [ebp - 0x68]
            //   51                   | push                ecx
            //   56                   | push                esi
            //   33db                 | xor                 ebx, ebx

        $sequence_8 = { e8???????? 83c408 33f6 8945f0 85ff }
            // n = 5, score = 2200
            //   e8????????           |                     
            //   83c408               | add                 esp, 8
            //   33f6                 | xor                 esi, esi
            //   8945f0               | mov                 dword ptr [ebp - 0x10], eax
            //   85ff                 | test                edi, edi

        $sequence_9 = { 55 8bec 8b5508 668b4510 8b4d0c 66894202 33c0 }
            // n = 7, score = 2200
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   8b5508               | mov                 edx, dword ptr [ebp + 8]
            //   668b4510             | mov                 ax, word ptr [ebp + 0x10]
            //   8b4d0c               | mov                 ecx, dword ptr [ebp + 0xc]
            //   66894202             | mov                 word ptr [edx + 2], ax
            //   33c0                 | xor                 eax, eax

    condition:
        7 of them and filesize < 371712
}

rule win_formbook_w0 {
    meta:
        author = "@malgamy12"
        date = "2022-11-8"
	    license = "DRL 1.1"
        sample1 = "9fc57307d1cce6f6d8946a7dae41447b"
        sample2 = "0f4a7fa6e654b48c0334b8b88410eaed"
        sample3 = "0a25d588340300461738a677d0b53cd2"
        sample4 = "57d7bd215e4c4d03d73addec72936334"
        sample5 = "c943e31f7927683dc1b628f0972e801b"
        sample6 = "db87f238bb4e972ef8c0b94779798fa9"
        sample7 = "8ba1449ee35200556ecd88f23a35863a"
        sample8 = "8ca20642318337816d5db9666e004172"
        sample9 = "280f7c87c98346102980c514d2dd25c8"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.formbook"
        malpedia_rule_date = "20230118"
        malpedia_hash = ""
        malpedia_version = "20230118"
        malpedia_license = "DRL 1.1"
        malpedia_sharing = "TLP:WHITE"
    strings:
        $a1 = { 8B 45 ?? BA ?? [3] 8B CF D3 E2 84 14 03 74 ?? 8B 4D ?? 31 0E 8B 55 ?? 31 56 ?? 8B 4D ?? 8B 55 ?? 31 4E ?? 31 56 ?? }
			
        $a2 = { 0F B6 3A 8B C8 C1 E9 ?? 33 CF 81 E1 [4] C1 E0 ?? 33 84 8D [4] 42 4E }
        
        $a3 = { 1A D2 80 E2 ?? 80 C2 ?? EB ?? 80 FA ?? 75 ?? 8A D0 80 E2 ?? }

        $a4 = { 80 E2 ?? F6 DA 1A D2 80 E2 ?? 80 C2 ?? }

    condition:
         3 of them
}