SYMBOLCOMMON_NAMEaka. SYNONYMS
win.unidentified_081 (Back to overview)

Unidentified 081 (Andariel Ransomware)

Actor(s): Silent Chollima


Kaspersky Labs observed Andariel to drop this ransomware in one case within a series of attacks carried out against targets in South Korea in April 2021.

References
2021-06-15KasperskySeongsu Park
@online{park:20210615:andariel:1e000a0, author = {Seongsu Park}, title = {{Andariel evolves to target South Korea with ransomware}}, date = {2021-06-15}, organization = {Kaspersky}, url = {https://securelist.com/andariel-evolves-to-target-south-korea-with-ransomware/102811/}, language = {English}, urldate = {2021-11-03} } Andariel evolves to target South Korea with ransomware
BISTROMATH PEBBLEDASH Tiger RAT Unidentified 081 (Andariel Ransomware)
Yara Rules
[TLP:WHITE] win_unidentified_081_auto (20230125 | Detects win.unidentified_081.)
rule win_unidentified_081_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        version = "1"
        description = "Detects win.unidentified_081."
        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.unidentified_081"
        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 = { 8bc1 be10000000 83e00f 2bf0 8d0439 }
            // n = 5, score = 100
            //   8bc1                 | mov                 eax, ecx
            //   be10000000           | mov                 esi, 0x10
            //   83e00f               | and                 eax, 0xf
            //   2bf0                 | sub                 esi, eax
            //   8d0439               | lea                 eax, [ecx + edi]

        $sequence_1 = { 8a8910964100 884dfe 8bcb c1e902 32b100954100 }
            // n = 5, score = 100
            //   8a8910964100         | mov                 cl, byte ptr [ecx + 0x419610]
            //   884dfe               | mov                 byte ptr [ebp - 2], cl
            //   8bcb                 | mov                 ecx, ebx
            //   c1e902               | shr                 ecx, 2
            //   32b100954100         | xor                 dh, byte ptr [ecx + 0x419500]

        $sequence_2 = { 8d901cb74100 5f 668b02 8d5202 668901 8d4902 4f }
            // n = 7, score = 100
            //   8d901cb74100         | lea                 edx, [eax + 0x41b71c]
            //   5f                   | pop                 edi
            //   668b02               | mov                 ax, word ptr [edx]
            //   8d5202               | lea                 edx, [edx + 2]
            //   668901               | mov                 word ptr [ecx], ax
            //   8d4902               | lea                 ecx, [ecx + 2]
            //   4f                   | dec                 edi

        $sequence_3 = { 83c404 b001 5e 5f 5b c3 }
            // n = 6, score = 100
            //   83c404               | add                 esp, 4
            //   b001                 | mov                 al, 1
            //   5e                   | pop                 esi
            //   5f                   | pop                 edi
            //   5b                   | pop                 ebx
            //   c3                   | ret                 

        $sequence_4 = { 8855ff 886dfe f6c303 7542 0fb6c9 8ad6 8ab110964100 }
            // n = 7, score = 100
            //   8855ff               | mov                 byte ptr [ebp - 1], dl
            //   886dfe               | mov                 byte ptr [ebp - 2], ch
            //   f6c303               | test                bl, 3
            //   7542                 | jne                 0x44
            //   0fb6c9               | movzx               ecx, cl
            //   8ad6                 | mov                 dl, dh
            //   8ab110964100         | mov                 dh, byte ptr [ecx + 0x419610]

        $sequence_5 = { 57 e8???????? 8bb52cffffff 83c404 }
            // n = 4, score = 100
            //   57                   | push                edi
            //   e8????????           |                     
            //   8bb52cffffff         | mov                 esi, dword ptr [ebp - 0xd4]
            //   83c404               | add                 esp, 4

        $sequence_6 = { 2bce d1f9 83f918 740a 68???????? e9???????? }
            // n = 6, score = 100
            //   2bce                 | sub                 ecx, esi
            //   d1f9                 | sar                 ecx, 1
            //   83f918               | cmp                 ecx, 0x18
            //   740a                 | je                  0xc
            //   68????????           |                     
            //   e9????????           |                     

        $sequence_7 = { 75f5 2bca d1f9 83f920 0f85f4020000 }
            // n = 5, score = 100
            //   75f5                 | jne                 0xfffffff7
            //   2bca                 | sub                 ecx, edx
            //   d1f9                 | sar                 ecx, 1
            //   83f920               | cmp                 ecx, 0x20
            //   0f85f4020000         | jne                 0x2fa

        $sequence_8 = { c68533ffffff00 e8???????? f30f6f05???????? f30f7f45e8 8bff 6a00 8d8534ffffff }
            // n = 7, score = 100
            //   c68533ffffff00       | mov                 byte ptr [ebp - 0xcd], 0
            //   e8????????           |                     
            //   f30f6f05????????     |                     
            //   f30f7f45e8           | movdqu              xmmword ptr [ebp - 0x18], xmm0
            //   8bff                 | mov                 edi, edi
            //   6a00                 | push                0
            //   8d8534ffffff         | lea                 eax, [ebp - 0xcc]

        $sequence_9 = { 898d3ce5ffff 8b8d24e5ffff 8b0485d0d14100 ff3401 ff15???????? 85c0 0f84ee020000 }
            // n = 7, score = 100
            //   898d3ce5ffff         | mov                 dword ptr [ebp - 0x1ac4], ecx
            //   8b8d24e5ffff         | mov                 ecx, dword ptr [ebp - 0x1adc]
            //   8b0485d0d14100       | mov                 eax, dword ptr [eax*4 + 0x41d1d0]
            //   ff3401               | push                dword ptr [ecx + eax]
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax
            //   0f84ee020000         | je                  0x2f4

    condition:
        7 of them and filesize < 273408
}
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