SYMBOLCOMMON_NAMEaka. SYNONYMS
win.cryptomix (Back to overview)

CryptoMix

aka: CryptFile2

A variant of CryptoMix is win.clop.

References
2020-03-04SentinelOneJason Reaves
@online{reaves:20200304:breaking:8262e7e, author = {Jason Reaves}, title = {{Breaking TA505’s Crypter with an SMT Solver}}, date = {2020-03-04}, organization = {SentinelOne}, url = {https://labs.sentinelone.com/breaking-ta505s-crypter-with-an-smt-solver/}, language = {English}, urldate = {2020-03-04} } Breaking TA505’s Crypter with an SMT Solver
Clop CryptoMix MINEBIDGE
2017-12-13Bleeping ComputerLawrence Abrams
@online{abrams:20171213:work:d439b4b, author = {Lawrence Abrams}, title = {{WORK Cryptomix Ransomware Variant Released}}, date = {2017-12-13}, organization = {Bleeping Computer}, url = {https://www.bleepingcomputer.com/news/security/work-cryptomix-ransomware-variant-released/}, language = {English}, urldate = {2019-12-20} } WORK Cryptomix Ransomware Variant Released
CryptoMix
2017-01-04CERT.PLJarosław Jedynak
@online{jedynak:20170104:technical:9cf0ab7, author = {Jarosław Jedynak}, title = {{Technical analysis of CryptoMix/CryptFile2 ransomware}}, date = {2017-01-04}, organization = {CERT.PL}, url = {https://www.cert.pl/en/news/single/technical-analysis-of-cryptomixcryptfile2-ransomware/}, language = {English}, urldate = {2020-01-13} } Technical analysis of CryptoMix/CryptFile2 ransomware
CryptoMix
Yara Rules
[TLP:WHITE] win_cryptomix_auto (20201014 | autogenerated rule brought to you by yara-signator)
rule win_cryptomix_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2020-10-14"
        version = "1"
        description = "autogenerated rule brought to you by yara-signator"
        tool = "yara-signator v0.5.0"
        tool_config = "callsandjumps;datarefs;binvalue"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.cryptomix"
        malpedia_rule_date = "20201014"
        malpedia_hash = "a7e3bd57eaf12bf3ea29a863c041091ba3af9ac9"
        malpedia_version = "20201014"
        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 = { 85c0 0f878c000000 68???????? 56 e8???????? }
            // n = 5, score = 200
            //   85c0                 | test                eax, eax
            //   0f878c000000         | ja                  0x92
            //   68????????           |                     
            //   56                   | push                esi
            //   e8????????           |                     

        $sequence_1 = { 8bf7 c7450800010000 8a16 0fb6c3 fec3 0fb60408 }
            // n = 6, score = 200
            //   8bf7                 | mov                 esi, edi
            //   c7450800010000       | mov                 dword ptr [ebp + 8], 0x100
            //   8a16                 | mov                 dl, byte ptr [esi]
            //   0fb6c3               | movzx               eax, bl
            //   fec3                 | inc                 bl
            //   0fb60408             | movzx               eax, byte ptr [eax + ecx]

        $sequence_2 = { c785dcfbffff05010000 ff15???????? 668b8df4fdffff 33c0 8d95f4fdffff }
            // n = 5, score = 200
            //   c785dcfbffff05010000     | mov    dword ptr [ebp - 0x424], 0x105
            //   ff15????????         |                     
            //   668b8df4fdffff       | mov                 cx, word ptr [ebp - 0x20c]
            //   33c0                 | xor                 eax, eax
            //   8d95f4fdffff         | lea                 edx, [ebp - 0x20c]

        $sequence_3 = { 89bd90f9ffff 6a00 83f814 752b 8d8590efffff 50 }
            // n = 6, score = 200
            //   89bd90f9ffff         | mov                 dword ptr [ebp - 0x670], edi
            //   6a00                 | push                0
            //   83f814               | cmp                 eax, 0x14
            //   752b                 | jne                 0x2d
            //   8d8590efffff         | lea                 eax, [ebp - 0x1070]
            //   50                   | push                eax

        $sequence_4 = { 740c 8bc8 a3???????? e8???????? 53 56 }
            // n = 6, score = 200
            //   740c                 | je                  0xe
            //   8bc8                 | mov                 ecx, eax
            //   a3????????           |                     
            //   e8????????           |                     
            //   53                   | push                ebx
            //   56                   | push                esi

        $sequence_5 = { 50 ffd7 bfc9f0f081 57 53 e8???????? 83c414 }
            // n = 7, score = 200
            //   50                   | push                eax
            //   ffd7                 | call                edi
            //   bfc9f0f081           | mov                 edi, 0x81f0f0c9
            //   57                   | push                edi
            //   53                   | push                ebx
            //   e8????????           |                     
            //   83c414               | add                 esp, 0x14

        $sequence_6 = { 56 68???????? ffd7 8d8598f9ffff 50 }
            // n = 5, score = 200
            //   56                   | push                esi
            //   68????????           |                     
            //   ffd7                 | call                edi
            //   8d8598f9ffff         | lea                 eax, [ebp - 0x668]
            //   50                   | push                eax

        $sequence_7 = { eb17 57 e8???????? 68bdb5b88f 6a08 }
            // n = 5, score = 200
            //   eb17                 | jmp                 0x19
            //   57                   | push                edi
            //   e8????????           |                     
            //   68bdb5b88f           | push                0x8fb8b5bd
            //   6a08                 | push                8

        $sequence_8 = { 683f000f00 56 56 56 68???????? 53 ffd0 }
            // n = 7, score = 200
            //   683f000f00           | push                0xf003f
            //   56                   | push                esi
            //   56                   | push                esi
            //   56                   | push                esi
            //   68????????           |                     
            //   53                   | push                ebx
            //   ffd0                 | call                eax

        $sequence_9 = { 745d ff75fc e8???????? ff75fc e8???????? 68f097a090 6a05 }
            // n = 7, score = 200
            //   745d                 | je                  0x5f
            //   ff75fc               | push                dword ptr [ebp - 4]
            //   e8????????           |                     
            //   ff75fc               | push                dword ptr [ebp - 4]
            //   e8????????           |                     
            //   68f097a090           | push                0x90a097f0
            //   6a05                 | push                5

        $sequence_10 = { 668945f4 660fd645e4 f30f7e05???????? 6a00 }
            // n = 4, score = 200
            //   668945f4             | mov                 word ptr [ebp - 0xc], ax
            //   660fd645e4           | movq                qword ptr [ebp - 0x1c], xmm0
            //   f30f7e05????????     |                     
            //   6a00                 | push                0

        $sequence_11 = { 8b3d???????? 83c40c 56 68???????? }
            // n = 4, score = 200
            //   8b3d????????         |                     
            //   83c40c               | add                 esp, 0xc
            //   56                   | push                esi
            //   68????????           |                     

        $sequence_12 = { 8b9db8f9ffff 68???????? 7507 68???????? eb05 68???????? }
            // n = 6, score = 200
            //   8b9db8f9ffff         | mov                 ebx, dword ptr [ebp - 0x648]
            //   68????????           |                     
            //   7507                 | jne                 9
            //   68????????           |                     
            //   eb05                 | jmp                 7
            //   68????????           |                     

        $sequence_13 = { 57 57 6a50 ff7514 }
            // n = 4, score = 200
            //   57                   | push                edi
            //   57                   | push                edi
            //   6a50                 | push                0x50
            //   ff7514               | push                dword ptr [ebp + 0x14]

        $sequence_14 = { 33c0 33ff 6805ad890d 47 57 8945f0 }
            // n = 6, score = 200
            //   33c0                 | xor                 eax, eax
            //   33ff                 | xor                 edi, edi
            //   6805ad890d           | push                0xd89ad05
            //   47                   | inc                 edi
            //   57                   | push                edi
            //   8945f0               | mov                 dword ptr [ebp - 0x10], eax

        $sequence_15 = { 6a08 eb35 83f804 7504 6a09 eb2c 385dfe }
            // n = 7, score = 200
            //   6a08                 | push                8
            //   eb35                 | jmp                 0x37
            //   83f804               | cmp                 eax, 4
            //   7504                 | jne                 6
            //   6a09                 | push                9
            //   eb2c                 | jmp                 0x2e
            //   385dfe               | cmp                 byte ptr [ebp - 2], bl

    condition:
        7 of them and filesize < 188416
}
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