SYMBOLCOMMON_NAMEaka. SYNONYMS
win.bleachgap (Back to overview)

BleachGap


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References
2022-08-25K7 SecurityGaurav Yaday
@online{yaday:20220825:bleachgap:ce2a832, author = {Gaurav Yaday}, title = {{BleachGap Revamped}}, date = {2022-08-25}, organization = {K7 Security}, url = {https://labs.k7computing.com/index.php/bleachgap-revamped/}, language = {English}, urldate = {2022-08-28} } BleachGap Revamped
BleachGap
Yara Rules
[TLP:WHITE] win_bleachgap_auto (20230125 | Detects win.bleachgap.)
rule win_bleachgap_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        version = "1"
        description = "Detects win.bleachgap."
        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.bleachgap"
        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 = { 8b94243c010000 0fa4c215 0facdf15 c1e015 c1fb15 8bcf 2bc8 }
            // n = 7, score = 100
            //   8b94243c010000       | mov                 edx, dword ptr [esp + 0x13c]
            //   0fa4c215             | shld                edx, eax, 0x15
            //   0facdf15             | shrd                edi, ebx, 0x15
            //   c1e015               | shl                 eax, 0x15
            //   c1fb15               | sar                 ebx, 0x15
            //   8bcf                 | mov                 ecx, edi
            //   2bc8                 | sub                 ecx, eax

        $sequence_1 = { 8be8 6a57 68???????? 55 e8???????? 83c40c 89442414 }
            // n = 7, score = 100
            //   8be8                 | mov                 ebp, eax
            //   6a57                 | push                0x57
            //   68????????           |                     
            //   55                   | push                ebp
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   89442414             | mov                 dword ptr [esp + 0x14], eax

        $sequence_2 = { 8b55f0 eb0a 894f24 c7432400000000 85d2 7440 8d45cc }
            // n = 7, score = 100
            //   8b55f0               | mov                 edx, dword ptr [ebp - 0x10]
            //   eb0a                 | jmp                 0xc
            //   894f24               | mov                 dword ptr [edi + 0x24], ecx
            //   c7432400000000       | mov                 dword ptr [ebx + 0x24], 0
            //   85d2                 | test                edx, edx
            //   7440                 | je                  0x42
            //   8d45cc               | lea                 eax, [ebp - 0x34]

        $sequence_3 = { c745fc00000000 bf01000000 660f1f440000 c745dc74000000 c645e05a c645e100 c645e20c }
            // n = 7, score = 100
            //   c745fc00000000       | mov                 dword ptr [ebp - 4], 0
            //   bf01000000           | mov                 edi, 1
            //   660f1f440000         | nop                 word ptr [eax + eax]
            //   c745dc74000000       | mov                 dword ptr [ebp - 0x24], 0x74
            //   c645e05a             | mov                 byte ptr [ebp - 0x20], 0x5a
            //   c645e100             | mov                 byte ptr [ebp - 0x1f], 0
            //   c645e20c             | mov                 byte ptr [ebp - 0x1e], 0xc

        $sequence_4 = { 8b4df8 8b5508 8bc2 25ff0f0000 3df00f0000 775f 660f3a63020d }
            // n = 7, score = 100
            //   8b4df8               | mov                 ecx, dword ptr [ebp - 8]
            //   8b5508               | mov                 edx, dword ptr [ebp + 8]
            //   8bc2                 | mov                 eax, edx
            //   25ff0f0000           | and                 eax, 0xfff
            //   3df00f0000           | cmp                 eax, 0xff0
            //   775f                 | ja                  0x61
            //   660f3a63020d         | pcmpistri           xmm0, xmmword ptr [edx], 0xd

        $sequence_5 = { e8???????? 83c408 85c0 0f8482030000 8d442418 50 6872100000 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   83c408               | add                 esp, 8
            //   85c0                 | test                eax, eax
            //   0f8482030000         | je                  0x388
            //   8d442418             | lea                 eax, [esp + 0x18]
            //   50                   | push                eax
            //   6872100000           | push                0x1072

        $sequence_6 = { e8???????? 83c40c 85c0 0f8490030000 56 e8???????? 8bf0 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   85c0                 | test                eax, eax
            //   0f8490030000         | je                  0x396
            //   56                   | push                esi
            //   e8????????           |                     
            //   8bf0                 | mov                 esi, eax

        $sequence_7 = { 8bf0 85f6 7f4d eb24 8139f6000000 7510 6a00 }
            // n = 7, score = 100
            //   8bf0                 | mov                 esi, eax
            //   85f6                 | test                esi, esi
            //   7f4d                 | jg                  0x4f
            //   eb24                 | jmp                 0x26
            //   8139f6000000         | cmp                 dword ptr [ecx], 0xf6
            //   7510                 | jne                 0x12
            //   6a00                 | push                0

        $sequence_8 = { c1c907 894c244c 8b8c2490000000 03cb 03d1 8b4c2470 8bfa }
            // n = 7, score = 100
            //   c1c907               | ror                 ecx, 7
            //   894c244c             | mov                 dword ptr [esp + 0x4c], ecx
            //   8b8c2490000000       | mov                 ecx, dword ptr [esp + 0x90]
            //   03cb                 | add                 ecx, ebx
            //   03d1                 | add                 edx, ecx
            //   8b4c2470             | mov                 ecx, dword ptr [esp + 0x70]
            //   8bfa                 | mov                 edi, edx

        $sequence_9 = { c1fb15 2bc8 899c24cc000000 1bda 8b542434 03d1 8b4c2444 }
            // n = 7, score = 100
            //   c1fb15               | sar                 ebx, 0x15
            //   2bc8                 | sub                 ecx, eax
            //   899c24cc000000       | mov                 dword ptr [esp + 0xcc], ebx
            //   1bda                 | sbb                 ebx, edx
            //   8b542434             | mov                 edx, dword ptr [esp + 0x34]
            //   03d1                 | add                 edx, ecx
            //   8b4c2444             | mov                 ecx, dword ptr [esp + 0x44]

    condition:
        7 of them and filesize < 4538368
}
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