SYMBOLCOMMON_NAMEaka. SYNONYMS
win.unidentified_088 (Back to overview)

Unidentified 088 (Nim Ransomware)


Ransomware written in Nim.

References
2021-10-14Medium walmartglobaltechJason Reaves
@online{reaves:20211014:investigation:29ef29c, author = {Jason Reaves}, title = {{Investigation into the state of NIM malware Part 2}}, date = {2021-10-14}, organization = {Medium walmartglobaltech}, url = {https://medium.com/walmartglobaltech/investigation-into-the-state-of-nim-malware-part-2-a28bffffa671}, language = {English}, urldate = {2021-12-15} } Investigation into the state of NIM malware Part 2
Cobalt Strike NimGrabber Nimrev Unidentified 088 (Nim Ransomware)
Yara Rules
[TLP:WHITE] win_unidentified_088_auto (20230715 | Detects win.unidentified_088.)
rule win_unidentified_088_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.unidentified_088."
        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_088"
        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 = { e8???????? 8b45dc 897de0 8945e4 eb3e 3b13 }
            // n = 6, score = 100
            //   e8????????           |                     
            //   8b45dc               | mov                 eax, dword ptr [ebp - 0x24]
            //   897de0               | mov                 dword ptr [ebp - 0x20], edi
            //   8945e4               | mov                 dword ptr [ebp - 0x1c], eax
            //   eb3e                 | jmp                 0x40
            //   3b13                 | cmp                 edx, dword ptr [ebx]

        $sequence_1 = { c705????????c08c4200 c705????????00000000 c605????????02 c705????????c8014200 c705????????1c000000 c705????????04000000 }
            // n = 6, score = 100
            //   c705????????c08c4200     |     
            //   c705????????00000000     |     
            //   c605????????02       |                     
            //   c705????????c8014200     |     
            //   c705????????1c000000     |     
            //   c705????????04000000     |     

        $sequence_2 = { c3 c3 55 89c1 89e5 }
            // n = 5, score = 100
            //   c3                   | ret                 
            //   c3                   | ret                 
            //   55                   | push                ebp
            //   89c1                 | mov                 ecx, eax
            //   89e5                 | mov                 ebp, esp

        $sequence_3 = { 83c8ff 8d4de4 89da e8???????? 84c0 745d e8???????? }
            // n = 7, score = 100
            //   83c8ff               | or                  eax, 0xffffffff
            //   8d4de4               | lea                 ecx, [ebp - 0x1c]
            //   89da                 | mov                 edx, ebx
            //   e8????????           |                     
            //   84c0                 | test                al, al
            //   745d                 | je                  0x5f
            //   e8????????           |                     

        $sequence_4 = { 8b45dc 8b7dc4 8a540708 80fa5c 7405 80fa2f 751e }
            // n = 7, score = 100
            //   8b45dc               | mov                 eax, dword ptr [ebp - 0x24]
            //   8b7dc4               | mov                 edi, dword ptr [ebp - 0x3c]
            //   8a540708             | mov                 dl, byte ptr [edi + eax + 8]
            //   80fa5c               | cmp                 dl, 0x5c
            //   7405                 | je                  7
            //   80fa2f               | cmp                 dl, 0x2f
            //   751e                 | jne                 0x20

        $sequence_5 = { 8945cc 0306 e8???????? 8d4de4 ba01000000 89f8 }
            // n = 6, score = 100
            //   8945cc               | mov                 dword ptr [ebp - 0x34], eax
            //   0306                 | add                 eax, dword ptr [esi]
            //   e8????????           |                     
            //   8d4de4               | lea                 ecx, [ebp - 0x1c]
            //   ba01000000           | mov                 edx, 1
            //   89f8                 | mov                 eax, edi

        $sequence_6 = { 56 53 81ecfc070000 a1???????? c744240400000000 8985b8f8ffff 8d85b8f8ffff }
            // n = 7, score = 100
            //   56                   | push                esi
            //   53                   | push                ebx
            //   81ecfc070000         | sub                 esp, 0x7fc
            //   a1????????           |                     
            //   c744240400000000     | mov                 dword ptr [esp + 4], 0
            //   8985b8f8ffff         | mov                 dword ptr [ebp - 0x748], eax
            //   8d85b8f8ffff         | lea                 eax, [ebp - 0x748]

        $sequence_7 = { 8b5508 2b13 e9???????? 894de0 e8???????? 394508 0f4d4508 }
            // n = 7, score = 100
            //   8b5508               | mov                 edx, dword ptr [ebp + 8]
            //   2b13                 | sub                 edx, dword ptr [ebx]
            //   e9????????           |                     
            //   894de0               | mov                 dword ptr [ebp - 0x20], ecx
            //   e8????????           |                     
            //   394508               | cmp                 dword ptr [ebp + 8], eax
            //   0f4d4508             | cmovge              eax, dword ptr [ebp + 8]

        $sequence_8 = { c21000 55 b9???????? 89e5 83ec08 e8???????? b9???????? }
            // n = 7, score = 100
            //   c21000               | ret                 0x10
            //   55                   | push                ebp
            //   b9????????           |                     
            //   89e5                 | mov                 ebp, esp
            //   83ec08               | sub                 esp, 8
            //   e8????????           |                     
            //   b9????????           |                     

        $sequence_9 = { 8945b0 8d45c0 e8???????? 8b03 }
            // n = 4, score = 100
            //   8945b0               | mov                 dword ptr [ebp - 0x50], eax
            //   8d45c0               | lea                 eax, [ebp - 0x40]
            //   e8????????           |                     
            //   8b03                 | mov                 eax, dword ptr [ebx]

    condition:
        7 of them and filesize < 919552
}
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