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 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
2017-01-04CERT.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 (20220411 | Detects win.cryptomix.)
rule win_cryptomix_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-04-08"
        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 = "20220405"
        malpedia_hash = "ecd38294bd47d5589be5cd5490dc8bb4804afc2a"
        malpedia_version = "20220411"
        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 = { 837d0c01 8b9db8f9ffff a1???????? 68???????? 7507 68???????? }
            // n = 6, score = 200
            //   837d0c01             | cmp                 dword ptr [ebp + 0xc], 1
            //   8b9db8f9ffff         | mov                 ebx, dword ptr [ebp - 0x648]
            //   a1????????           |                     
            //   68????????           |                     
            //   7507                 | jne                 9
            //   68????????           |                     

        $sequence_1 = { 6a00 89bd90f9ffff 6a00 83f814 }
            // n = 4, score = 200
            //   6a00                 | push                0
            //   89bd90f9ffff         | mov                 dword ptr [ebp - 0x670], edi
            //   6a00                 | push                0
            //   83f814               | cmp                 eax, 0x14

        $sequence_2 = { 6871a15e72 6a01 e8???????? 59 59 6800200000 }
            // n = 6, score = 200
            //   6871a15e72           | push                0x725ea171
            //   6a01                 | push                1
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx
            //   6800200000           | push                0x2000

        $sequence_3 = { 50 ff15???????? c705????????00000000 eb28 40 a3???????? 8d8590efffff }
            // n = 7, score = 200
            //   50                   | push                eax
            //   ff15????????         |                     
            //   c705????????00000000     |     
            //   eb28                 | jmp                 0x2a
            //   40                   | inc                 eax
            //   a3????????           |                     
            //   8d8590efffff         | lea                 eax, dword ptr [ebp - 0x1070]

        $sequence_4 = { 7715 68???????? 56 e8???????? 59 59 }
            // n = 6, score = 200
            //   7715                 | ja                  0x17
            //   68????????           |                     
            //   56                   | push                esi
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx

        $sequence_5 = { 59 59 8d4dfc 51 6801000008 6a02 }
            // n = 6, score = 200
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx
            //   8d4dfc               | lea                 ecx, dword ptr [ebp - 4]
            //   51                   | push                ecx
            //   6801000008           | push                0x8000001
            //   6a02                 | push                2

        $sequence_6 = { 59 eb11 e8???????? 59 }
            // n = 4, score = 200
            //   59                   | pop                 ecx
            //   eb11                 | jmp                 0x13
            //   e8????????           |                     
            //   59                   | pop                 ecx

        $sequence_7 = { 68???????? 8d85e8fbffff 50 ffd7 8d85c4f9ffff 50 }
            // n = 6, score = 200
            //   68????????           |                     
            //   8d85e8fbffff         | lea                 eax, dword ptr [ebp - 0x418]
            //   50                   | push                eax
            //   ffd7                 | call                edi
            //   8d85c4f9ffff         | lea                 eax, dword ptr [ebp - 0x63c]
            //   50                   | push                eax

        $sequence_8 = { 68???????? 8d85c4f9ffff 50 ffd6 85c0 0f8554010000 68???????? }
            // n = 7, score = 200
            //   68????????           |                     
            //   8d85c4f9ffff         | lea                 eax, dword ptr [ebp - 0x63c]
            //   50                   | push                eax
            //   ffd6                 | call                esi
            //   85c0                 | test                eax, eax
            //   0f8554010000         | jne                 0x15a
            //   68????????           |                     

        $sequence_9 = { 683f020f00 56 68???????? bb01000080 53 }
            // n = 5, score = 200
            //   683f020f00           | push                0xf023f
            //   56                   | push                esi
            //   68????????           |                     
            //   bb01000080           | mov                 ebx, 0x80000001
            //   53                   | push                ebx

        $sequence_10 = { 50 c785e0fbffff05010000 ff15???????? 668b85f4fdffff 33c9 8d95f4fdffff 6685c0 }
            // n = 7, score = 200
            //   50                   | push                eax
            //   c785e0fbffff05010000     | mov    dword ptr [ebp - 0x420], 0x105
            //   ff15????????         |                     
            //   668b85f4fdffff       | mov                 ax, word ptr [ebp - 0x20c]
            //   33c9                 | xor                 ecx, ecx
            //   8d95f4fdffff         | lea                 edx, dword ptr [ebp - 0x20c]
            //   6685c0               | test                ax, ax

        $sequence_11 = { 6a02 8bf8 58 6875f79b8e 6a08 668945f0 }
            // n = 6, score = 200
            //   6a02                 | push                2
            //   8bf8                 | mov                 edi, eax
            //   58                   | pop                 eax
            //   6875f79b8e           | push                0x8e9bf775
            //   6a08                 | push                8
            //   668945f0             | mov                 word ptr [ebp - 0x10], ax

        $sequence_12 = { c3 68f0767c2a 6a04 e8???????? }
            // n = 4, score = 200
            //   c3                   | ret                 
            //   68f0767c2a           | push                0x2a7c76f0
            //   6a04                 | push                4
            //   e8????????           |                     

        $sequence_13 = { 6a00 ff15???????? 6896000000 ff15???????? 8b9d80efffff }
            // n = 5, score = 200
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   6896000000           | push                0x96
            //   ff15????????         |                     
            //   8b9d80efffff         | mov                 ebx, dword ptr [ebp - 0x1080]

        $sequence_14 = { 899584efffff 89b58cefffff 898588efffff ff15???????? 6808020000 }
            // n = 5, score = 200
            //   899584efffff         | mov                 dword ptr [ebp - 0x107c], edx
            //   89b58cefffff         | mov                 dword ptr [ebp - 0x1074], esi
            //   898588efffff         | mov                 dword ptr [ebp - 0x1078], eax
            //   ff15????????         |                     
            //   6808020000           | push                0x208

        $sequence_15 = { 83ec10 57 33ff 6822ded78a }
            // n = 4, score = 200
            //   83ec10               | sub                 esp, 0x10
            //   57                   | push                edi
            //   33ff                 | xor                 edi, edi
            //   6822ded78a           | push                0x8ad7de22

    condition:
        7 of them and filesize < 188416
}
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