SYMBOLCOMMON_NAMEaka. SYNONYMS
win.mistcloak (Back to overview)

MISTCLOAK


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 (20230125 | Detects win.mistcloak.)
rule win_mistcloak_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        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 = "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 = { 56 8b048590500110 8b7508 57 8bfe 8b440818 }
            // n = 6, score = 100
            //   56                   | push                esi
            //   8b048590500110       | mov                 eax, dword ptr [eax*4 + 0x10015090]
            //   8b7508               | mov                 esi, dword ptr [ebp + 8]
            //   57                   | push                edi
            //   8bfe                 | mov                 edi, esi
            //   8b440818             | mov                 eax, dword ptr [eax + ecx + 0x18]

        $sequence_1 = { 8b4dd8 83c40c 8b55dc 8b7db4 8bf3 8b04bd90500110 }
            // n = 6, score = 100
            //   8b4dd8               | mov                 ecx, dword ptr [ebp - 0x28]
            //   83c40c               | add                 esp, 0xc
            //   8b55dc               | mov                 edx, dword ptr [ebp - 0x24]
            //   8b7db4               | mov                 edi, dword ptr [ebp - 0x4c]
            //   8bf3                 | mov                 esi, ebx
            //   8b04bd90500110       | mov                 eax, dword ptr [edi*4 + 0x10015090]

        $sequence_2 = { 8bc1 3914c5781a0110 7408 40 83f81d 7cf1 }
            // n = 6, score = 100
            //   8bc1                 | mov                 eax, ecx
            //   3914c5781a0110       | cmp                 dword ptr [eax*8 + 0x10011a78], edx
            //   7408                 | je                  0xa
            //   40                   | inc                 eax
            //   83f81d               | cmp                 eax, 0x1d
            //   7cf1                 | jl                  0xfffffff3

        $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 = { 90 90 8d45c0 6a32 }
            // n = 4, score = 100
            //   90                   | nop                 
            //   90                   | nop                 
            //   8d45c0               | lea                 eax, [ebp - 0x40]
            //   6a32                 | push                0x32

        $sequence_8 = { 83e63f c1f906 6bf638 8b0c8d90500110 }
            // n = 4, score = 100
            //   83e63f               | and                 esi, 0x3f
            //   c1f906               | sar                 ecx, 6
            //   6bf638               | imul                esi, esi, 0x38
            //   8b0c8d90500110       | mov                 ecx, dword ptr [ecx*4 + 0x10015090]

        $sequence_9 = { 58 8b55f8 33c9 837dfc32 8b75f4 }
            // n = 5, score = 100
            //   58                   | pop                 eax
            //   8b55f8               | mov                 edx, dword ptr [ebp - 8]
            //   33c9                 | xor                 ecx, ecx
            //   837dfc32             | cmp                 dword ptr [ebp - 4], 0x32
            //   8b75f4               | mov                 esi, dword ptr [ebp - 0xc]

    condition:
        7 of them and filesize < 196608
}
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