rule win_blister_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-12-06"
        version = "1"
        description = "Detects win.blister."
        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.blister"
        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 = { 33f6 8d4447fe 8975fc 8945f8 3bfe 0f8447010000 }
            // n = 6, score = 100
            //   33f6                 | xor                 esi, esi
            //   8d4447fe             | lea                 eax, [edi + eax*2 - 2]
            //   8975fc               | mov                 dword ptr [ebp - 4], esi
            //   8945f8               | mov                 dword ptr [ebp - 8], eax
            //   3bfe                 | cmp                 edi, esi
            //   0f8447010000         | je                  0x14d

        $sequence_1 = { 57 ff75fc ffd6 85c0 7529 33c9 41 }
            // n = 7, score = 100
            //   57                   | push                edi
            //   ff75fc               | push                dword ptr [ebp - 4]
            //   ffd6                 | call                esi
            //   85c0                 | test                eax, eax
            //   7529                 | jne                 0x2b
            //   33c9                 | xor                 ecx, ecx
            //   41                   | inc                 ecx

        $sequence_2 = { e8???????? 8bf0 85f6 7c2e 6a04 58 8d4d08 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   8bf0                 | mov                 esi, eax
            //   85f6                 | test                esi, esi
            //   7c2e                 | jl                  0x30
            //   6a04                 | push                4
            //   58                   | pop                 eax
            //   8d4d08               | lea                 ecx, [ebp + 8]

        $sequence_3 = { 8bff 55 8bec b8dc140000 e8???????? a1???????? 33c5 }
            // n = 7, score = 100
            //   8bff                 | mov                 edi, edi
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   b8dc140000           | mov                 eax, 0x14dc
            //   e8????????           |                     
            //   a1????????           |                     
            //   33c5                 | xor                 eax, ebp

        $sequence_4 = { 8b3d???????? 6870010000 684c040000 ff7604 ffd7 8b1d???????? }
            // n = 6, score = 100
            //   8b3d????????         |                     
            //   6870010000           | push                0x170
            //   684c040000           | push                0x44c
            //   ff7604               | push                dword ptr [esi + 4]
            //   ffd7                 | call                edi
            //   8b1d????????         |                     

        $sequence_5 = { 8d45a0 50 ff750c c745a060000000 6891100000 ff36 }
            // n = 6, score = 100
            //   8d45a0               | lea                 eax, [ebp - 0x60]
            //   50                   | push                eax
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   c745a060000000       | mov                 dword ptr [ebp - 0x60], 0x60
            //   6891100000           | push                0x1091
            //   ff36                 | push                dword ptr [esi]

        $sequence_6 = { ff7604 ff75f4 ff75e8 6a02 ff75fc ff15???????? 85c0 }
            // n = 7, score = 100
            //   ff7604               | push                dword ptr [esi + 4]
            //   ff75f4               | push                dword ptr [ebp - 0xc]
            //   ff75e8               | push                dword ptr [ebp - 0x18]
            //   6a02                 | push                2
            //   ff75fc               | push                dword ptr [ebp - 4]
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax

        $sequence_7 = { 8b4e28 8d45f8 50 895df8 e8???????? }
            // n = 5, score = 100
            //   8b4e28               | mov                 ecx, dword ptr [esi + 0x28]
            //   8d45f8               | lea                 eax, [ebp - 8]
            //   50                   | push                eax
            //   895df8               | mov                 dword ptr [ebp - 8], ebx
            //   e8????????           |                     

        $sequence_8 = { ff15???????? 8bc8 0fb701 f7d8 1bc0 23c1 5e }
            // n = 7, score = 100
            //   ff15????????         |                     
            //   8bc8                 | mov                 ecx, eax
            //   0fb701               | movzx               eax, word ptr [ecx]
            //   f7d8                 | neg                 eax
            //   1bc0                 | sbb                 eax, eax
            //   23c1                 | and                 eax, ecx
            //   5e                   | pop                 esi

        $sequence_9 = { 50 8b859cf7ffff 8b8c052cf7ffff e8???????? 8985a8f7ffff 85c0 0f8cf9010000 }
            // n = 7, score = 100
            //   50                   | push                eax
            //   8b859cf7ffff         | mov                 eax, dword ptr [ebp - 0x864]
            //   8b8c052cf7ffff       | mov                 ecx, dword ptr [ebp + eax - 0x8d4]
            //   e8????????           |                     
            //   8985a8f7ffff         | mov                 dword ptr [ebp - 0x858], eax
            //   85c0                 | test                eax, eax
            //   0f8cf9010000         | jl                  0x1ff

    condition:
        7 of them and filesize < 1822720
}

rule win_blister_w0 {
    meta:
        author = "Elastic Security"
        description = "Detects Blister loader."
        creation_date = "2021-12-20"
        last_modified = "2021-12-20"
        os = "Windows"
        category_type = "Trojan"
        family = "Blister"
        threat_name = "Windows.Trojan.Blister"
        reference_sample = "0a7778cf6f9a1bd894e89f282f2e40f9d6c9cd4b72be97328e681fe32a1b1a00"
        source = "https://www.elastic.co/de/blog/elastic-security-uncovers-blister-malware-campaign"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.blister"
        malpedia_rule_date = "20211223"
        malpedia_hash = ""
        malpedia_version = "20211223"
        malpedia_sharing = "TLP:WHITE"

    strings:
        $a1 = {8D 45 DC 89 5D EC 50 6A 04 8D 45 F0 50 8D 45 EC 50 6A FF FF D7}
        $a2 = {75 F7 39 4D FC 0F 85 F3 00 00 00 64 A1 30 00 00 00 53 57 89 75}           
condition:
        any of them
}