SYMBOLCOMMON_NAMEaka. SYNONYMS
win.mistcloak (Back to overview)

MISTCLOAK

aka: HIUPAN

Mandiant associates this with UNC4191, this malware decrypts and runs DARKDEW.

References
2022-11-28MandiantRyan Tomcik, John Wolfram, Tommy Dacanay, Geoff Ackerman
@online{tomcik:20221128:always:f073a0d, author = {Ryan Tomcik and John Wolfram and Tommy Dacanay and Geoff Ackerman}, title = {{Always Another Secret: Lifting the Haze on China-nexus Espionage in Southeast Asia}}, date = {2022-11-28}, organization = {Mandiant}, url = {https://www.mandiant.com/resources/blog/china-nexus-espionage-southeast-asia}, language = {English}, urldate = {2022-12-02} } Always Another Secret: Lifting the Haze on China-nexus Espionage in Southeast Asia
BLUEHAZE DARKDEW MISTCLOAK
2022-11-03SophosGabor Szappanos
@online{szappanos:20221103:family:666a56f, author = {Gabor Szappanos}, title = {{Family Tree: DLL-Sideloading Cases May Be Related}}, date = {2022-11-03}, organization = {Sophos}, url = {https://news.sophos.com/en-us/2022/11/03/family-tree-dll-sideloading-cases-may-be-related/}, language = {English}, urldate = {2022-12-02} } Family Tree: DLL-Sideloading Cases May Be Related
DARKDEW MISTCLOAK
Yara Rules
[TLP:WHITE] win_mistcloak_auto (20230715 | Detects win.mistcloak.)
rule win_mistcloak_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.mistcloak."
        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.mistcloak"
        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 = { 83c410 83f8ff 0f8403020000 eb55 0fb607 0fbe8850470110 }
            // n = 6, score = 100
            //   83c410               | add                 esp, 0x10
            //   83f8ff               | cmp                 eax, -1
            //   0f8403020000         | je                  0x209
            //   eb55                 | jmp                 0x57
            //   0fb607               | movzx               eax, byte ptr [edi]
            //   0fbe8850470110       | movsx               ecx, byte ptr [eax + 0x10014750]

        $sequence_1 = { 7e25 8bf1 8b45b4 8b0c8590500110 8a043b 03ce 8b75dc }
            // n = 7, score = 100
            //   7e25                 | jle                 0x27
            //   8bf1                 | mov                 esi, ecx
            //   8b45b4               | mov                 eax, dword ptr [ebp - 0x4c]
            //   8b0c8590500110       | mov                 ecx, dword ptr [eax*4 + 0x10015090]
            //   8a043b               | mov                 al, byte ptr [ebx + edi]
            //   03ce                 | add                 ecx, esi
            //   8b75dc               | mov                 esi, dword ptr [ebp - 0x24]

        $sequence_2 = { ff15???????? 8b04bd90500110 834c0318ff 33c0 }
            // n = 4, score = 100
            //   ff15????????         |                     
            //   8b04bd90500110       | mov                 eax, dword ptr [edi*4 + 0x10015090]
            //   834c0318ff           | or                  dword ptr [ebx + eax + 0x18], 0xffffffff
            //   33c0                 | xor                 eax, eax

        $sequence_3 = { 8d1c8500500110 8b03 90 8b15???????? 83cfff 8bca }
            // n = 6, score = 100
            //   8d1c8500500110       | lea                 ebx, [eax*4 + 0x10015000]
            //   8b03                 | mov                 eax, dword ptr [ebx]
            //   90                   | nop                 
            //   8b15????????         |                     
            //   83cfff               | or                  edi, 0xffffffff
            //   8bca                 | mov                 ecx, edx

        $sequence_4 = { 83e73f c1f906 6bd738 8b0c8d90500110 c644112800 }
            // n = 5, score = 100
            //   83e73f               | and                 edi, 0x3f
            //   c1f906               | sar                 ecx, 6
            //   6bd738               | imul                edx, edi, 0x38
            //   8b0c8d90500110       | mov                 ecx, dword ptr [ecx*4 + 0x10015090]
            //   c644112800           | mov                 byte ptr [ecx + edx + 0x28], 0

        $sequence_5 = { 57 6a00 ff15???????? 8bf0 8d45c8 }
            // n = 5, score = 100
            //   57                   | push                edi
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   8bf0                 | mov                 esi, eax
            //   8d45c8               | lea                 eax, [ebp - 0x38]

        $sequence_6 = { 47 84c0 75f8 b911000000 8d85c4feffff be???????? }
            // n = 6, score = 100
            //   47                   | inc                 edi
            //   84c0                 | test                al, al
            //   75f8                 | jne                 0xfffffffa
            //   b911000000           | mov                 ecx, 0x11
            //   8d85c4feffff         | lea                 eax, [ebp - 0x13c]
            //   be????????           |                     

        $sequence_7 = { 660f6ec2 660f62d8 0f57c0 660f6ece 660f62ca }
            // n = 5, score = 100
            //   660f6ec2             | movd                xmm0, edx
            //   660f62d8             | punpckldq           xmm3, xmm0
            //   0f57c0               | xorps               xmm0, xmm0
            //   660f6ece             | movd                xmm1, esi
            //   660f62ca             | punpckldq           xmm1, xmm2

        $sequence_8 = { 83feff 7576 eb56 8b048558db0010 6800080000 6a00 50 }
            // n = 7, score = 100
            //   83feff               | cmp                 esi, -1
            //   7576                 | jne                 0x78
            //   eb56                 | jmp                 0x58
            //   8b048558db0010       | mov                 eax, dword ptr [eax*4 + 0x1000db58]
            //   6800080000           | push                0x800
            //   6a00                 | push                0
            //   50                   | push                eax

        $sequence_9 = { 660f6ece 660f62ca 660f62d9 660f3840dd }
            // n = 4, score = 100
            //   660f6ece             | movd                xmm1, esi
            //   660f62ca             | punpckldq           xmm1, xmm2
            //   660f62d9             | punpckldq           xmm3, xmm1
            //   660f3840dd           | pmulld              xmm3, xmm5

    condition:
        7 of them and filesize < 196608
}
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