SYMBOLCOMMON_NAMEaka. SYNONYMS
win.cryptomix (Back to overview)

CryptoMix

aka: Azer, 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 MINEBRIDGE
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
2017-07-05Bleeping ComputerLawrence Abrams
@online{abrams:20170705:new:f1fc004, author = {Lawrence Abrams}, title = {{New Azer CryptoMix Ransomware Variant Released}}, date = {2017-07-05}, organization = {Bleeping Computer}, url = {https://www.bleepingcomputer.com/news/security/new-azer-cryptomix-ransomware-variant-released/}, language = {English}, urldate = {2023-02-06} } New Azer 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 (20230715 | Detects win.cryptomix.)
rule win_cryptomix_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.cryptomix."
        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.cryptomix"
        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 = { 0fb7c9 8bff c1c007 0fb7c9 8d5202 33c1 0fb70a }
            // n = 7, score = 200
            //   0fb7c9               | movzx               ecx, cx
            //   8bff                 | mov                 edi, edi
            //   c1c007               | rol                 eax, 7
            //   0fb7c9               | movzx               ecx, cx
            //   8d5202               | lea                 edx, [edx + 2]
            //   33c1                 | xor                 eax, ecx
            //   0fb70a               | movzx               ecx, word ptr [edx]

        $sequence_1 = { c3 68e6b8402d 6a01 e8???????? 59 59 ff742404 }
            // n = 7, score = 200
            //   c3                   | ret                 
            //   68e6b8402d           | push                0x2d40b8e6
            //   6a01                 | push                1
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx
            //   ff742404             | push                dword ptr [esp + 4]

        $sequence_2 = { 53 ffd0 56 57 e8???????? 59 }
            // n = 6, score = 200
            //   53                   | push                ebx
            //   ffd0                 | call                eax
            //   56                   | push                esi
            //   57                   | push                edi
            //   e8????????           |                     
            //   59                   | pop                 ecx

        $sequence_3 = { 56 68???????? ffd7 8b1d???????? }
            // n = 4, score = 200
            //   56                   | push                esi
            //   68????????           |                     
            //   ffd7                 | call                edi
            //   8b1d????????         |                     

        $sequence_4 = { 7311 f30f7e0e 83e908 8d7608 660fd60f 8d7f08 8b048d48134000 }
            // n = 7, score = 200
            //   7311                 | jae                 0x13
            //   f30f7e0e             | movq                xmm1, qword ptr [esi]
            //   83e908               | sub                 ecx, 8
            //   8d7608               | lea                 esi, [esi + 8]
            //   660fd60f             | movq                qword ptr [edi], xmm1
            //   8d7f08               | lea                 edi, [edi + 8]
            //   8b048d48134000       | mov                 eax, dword ptr [ecx*4 + 0x401348]

        $sequence_5 = { ffd0 c3 55 8bec 6859c7ecd4 }
            // n = 5, score = 200
            //   ffd0                 | call                eax
            //   c3                   | ret                 
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   6859c7ecd4           | push                0xd4ecc759

        $sequence_6 = { 7723 74e4 3d3444babe 74dd }
            // n = 4, score = 200
            //   7723                 | ja                  0x25
            //   74e4                 | je                  0xffffffe6
            //   3d3444babe           | cmp                 eax, 0xbeba4434
            //   74dd                 | je                  0xffffffdf

        $sequence_7 = { 83f804 7414 83f806 740f 83f807 740a 83f808 }
            // n = 7, score = 200
            //   83f804               | cmp                 eax, 4
            //   7414                 | je                  0x16
            //   83f806               | cmp                 eax, 6
            //   740f                 | je                  0x11
            //   83f807               | cmp                 eax, 7
            //   740a                 | je                  0xc
            //   83f808               | cmp                 eax, 8

        $sequence_8 = { 8bcb e8???????? 83c408 56 ff15???????? }
            // n = 5, score = 200
            //   8bcb                 | mov                 ecx, ebx
            //   e8????????           |                     
            //   83c408               | add                 esp, 8
            //   56                   | push                esi
            //   ff15????????         |                     

        $sequence_9 = { 6a50 ffd0 ff7508 668945f2 e8???????? 59 ff7508 }
            // n = 7, score = 200
            //   6a50                 | push                0x50
            //   ffd0                 | call                eax
            //   ff7508               | push                dword ptr [ebp + 8]
            //   668945f2             | mov                 word ptr [ebp - 0xe], ax
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   ff7508               | push                dword ptr [ebp + 8]

        $sequence_10 = { 32ff 894dfc 66c787000100000000 33c0 8bd7 be00010000 8802 }
            // n = 7, score = 200
            //   32ff                 | xor                 bh, bh
            //   894dfc               | mov                 dword ptr [ebp - 4], ecx
            //   66c787000100000000     | mov    word ptr [edi + 0x100], 0
            //   33c0                 | xor                 eax, eax
            //   8bd7                 | mov                 edx, edi
            //   be00010000           | mov                 esi, 0x100
            //   8802                 | mov                 byte ptr [edx], al

        $sequence_11 = { 55 8bec 686a85139f 6a06 e8???????? }
            // n = 5, score = 200
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   686a85139f           | push                0x9f13856a
            //   6a06                 | push                6
            //   e8????????           |                     

        $sequence_12 = { ff75f8 ffd0 8945fc 3bc7 0f848c000000 }
            // n = 5, score = 200
            //   ff75f8               | push                dword ptr [ebp - 8]
            //   ffd0                 | call                eax
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   3bc7                 | cmp                 eax, edi
            //   0f848c000000         | je                  0x92

        $sequence_13 = { 33c0 33ff 6805ad890d 47 57 }
            // n = 5, score = 200
            //   33c0                 | xor                 eax, eax
            //   33ff                 | xor                 edi, edi
            //   6805ad890d           | push                0xd89ad05
            //   47                   | inc                 edi
            //   57                   | push                edi

        $sequence_14 = { 8d85e4fbffff 50 56 ff15???????? 8d85e8fbffff 50 }
            // n = 6, score = 200
            //   8d85e4fbffff         | lea                 eax, [ebp - 0x41c]
            //   50                   | push                eax
            //   56                   | push                esi
            //   ff15????????         |                     
            //   8d85e8fbffff         | lea                 eax, [ebp - 0x418]
            //   50                   | push                eax

        $sequence_15 = { 837d0c01 8b9db8f9ffff a1???????? 68???????? 7507 }
            // n = 5, score = 200
            //   837d0c01             | cmp                 dword ptr [ebp + 0xc], 1
            //   8b9db8f9ffff         | mov                 ebx, dword ptr [ebp - 0x648]
            //   a1????????           |                     
            //   68????????           |                     
            //   7507                 | jne                 9

    condition:
        7 of them and filesize < 188416
}
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