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 (20230125 | Detects win.cryptomix.)
rule win_cryptomix_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        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 = "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 = { 7727 747d 3d88acb255 7476 3d91e7ca58 }
            // n = 5, score = 200
            //   7727                 | ja                  0x29
            //   747d                 | je                  0x7f
            //   3d88acb255           | cmp                 eax, 0x55b2ac88
            //   7476                 | je                  0x78
            //   3d91e7ca58           | cmp                 eax, 0x58cae791

        $sequence_1 = { 68???????? 6a00 6a00 ffd0 6896000000 ff15???????? }
            // n = 6, score = 200
            //   68????????           |                     
            //   6a00                 | push                0
            //   6a00                 | push                0
            //   ffd0                 | call                eax
            //   6896000000           | push                0x96
            //   ff15????????         |                     

        $sequence_2 = { 7503 8b45f0 c9 c3 }
            // n = 4, score = 200
            //   7503                 | jne                 5
            //   8b45f0               | mov                 eax, dword ptr [ebp - 0x10]
            //   c9                   | leave               
            //   c3                   | ret                 

        $sequence_3 = { 6a08 e8???????? 59 59 6a00 6a01 }
            // n = 6, score = 200
            //   6a08                 | push                8
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx
            //   6a00                 | push                0
            //   6a01                 | push                1

        $sequence_4 = { 6804010000 6a40 ff15???????? 6804010000 8bf0 }
            // n = 5, score = 200
            //   6804010000           | push                0x104
            //   6a40                 | push                0x40
            //   ff15????????         |                     
            //   6804010000           | push                0x104
            //   8bf0                 | mov                 esi, eax

        $sequence_5 = { ffd0 c3 68c1ea9d27 6a01 e8???????? 59 59 }
            // n = 7, score = 200
            //   ffd0                 | call                eax
            //   c3                   | ret                 
            //   68c1ea9d27           | push                0x279deac1
            //   6a01                 | push                1
            //   e8????????           |                     
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx

        $sequence_6 = { 81ec14020000 53 56 57 68fe934377 6a01 e8???????? }
            // n = 7, score = 200
            //   81ec14020000         | sub                 esp, 0x214
            //   53                   | push                ebx
            //   56                   | push                esi
            //   57                   | push                edi
            //   68fe934377           | push                0x774393fe
            //   6a01                 | push                1
            //   e8????????           |                     

        $sequence_7 = { f30f7e05???????? 66a1???????? 660fd645dc f30f7e05???????? 6a00 }
            // n = 5, score = 200
            //   f30f7e05????????     |                     
            //   66a1????????         |                     
            //   660fd645dc           | movq                qword ptr [ebp - 0x24], xmm0
            //   f30f7e05????????     |                     
            //   6a00                 | push                0

        $sequence_8 = { c3 683adc703d 6a02 e8???????? }
            // n = 4, score = 200
            //   c3                   | ret                 
            //   683adc703d           | push                0x3d70dc3a
            //   6a02                 | push                2
            //   e8????????           |                     

        $sequence_9 = { 83c408 8d8598f9ffff 50 56 ff15???????? }
            // n = 5, score = 200
            //   83c408               | add                 esp, 8
            //   8d8598f9ffff         | lea                 eax, [ebp - 0x668]
            //   50                   | push                eax
            //   56                   | push                esi
            //   ff15????????         |                     

        $sequence_10 = { 57 ffd0 85c0 751d ff750c ff7508 }
            // n = 6, score = 200
            //   57                   | push                edi
            //   ffd0                 | call                eax
            //   85c0                 | test                eax, eax
            //   751d                 | jne                 0x1f
            //   ff750c               | push                dword ptr [ebp + 0xc]
            //   ff7508               | push                dword ptr [ebp + 8]

        $sequence_11 = { 56 56 68???????? 53 ffd0 8b45fc }
            // n = 6, score = 200
            //   56                   | push                esi
            //   56                   | push                esi
            //   68????????           |                     
            //   53                   | push                ebx
            //   ffd0                 | call                eax
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]

        $sequence_12 = { ffd6 85c0 0f850b010000 837d0c01 8b9db8f9ffff a1???????? 68???????? }
            // n = 7, score = 200
            //   ffd6                 | call                esi
            //   85c0                 | test                eax, eax
            //   0f850b010000         | jne                 0x111
            //   837d0c01             | cmp                 dword ptr [ebp + 0xc], 1
            //   8b9db8f9ffff         | mov                 ebx, dword ptr [ebp - 0x648]
            //   a1????????           |                     
            //   68????????           |                     

        $sequence_13 = { 59 8d8de8f9ffff 51 ffd0 }
            // n = 4, score = 200
            //   59                   | pop                 ecx
            //   8d8de8f9ffff         | lea                 ecx, [ebp - 0x618]
            //   51                   | push                ecx
            //   ffd0                 | call                eax

        $sequence_14 = { ffb5e8fbffff ff15???????? ffb5e8fbffff 8937 ff15???????? 8b4dfc 5f }
            // n = 7, score = 200
            //   ffb5e8fbffff         | push                dword ptr [ebp - 0x418]
            //   ff15????????         |                     
            //   ffb5e8fbffff         | push                dword ptr [ebp - 0x418]
            //   8937                 | mov                 dword ptr [edi], esi
            //   ff15????????         |                     
            //   8b4dfc               | mov                 ecx, dword ptr [ebp - 4]
            //   5f                   | pop                 edi

        $sequence_15 = { 6aff 50 ff15???????? c705????????00000000 eb1c 40 a3???????? }
            // n = 7, score = 200
            //   6aff                 | push                -1
            //   50                   | push                eax
            //   ff15????????         |                     
            //   c705????????00000000     |     
            //   eb1c                 | jmp                 0x1e
            //   40                   | inc                 eax
            //   a3????????           |                     

    condition:
        7 of them and filesize < 188416
}
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