SYMBOLCOMMON_NAMEaka. SYNONYMS
win.iispy (Back to overview)

IISpy

aka: BadIIS

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References
2021-08-09ESET ResearchZuzana Hromcová
@online{hromcov:20210809:iispy:c0b6ad3, author = {Zuzana Hromcová}, title = {{IISpy: A complex server‑side backdoor with anti‑forensic features}}, date = {2021-08-09}, organization = {ESET Research}, url = {https://www.welivesecurity.com/2021/08/09/iispy-complex-server-side-backdoor-antiforensic-features/}, language = {English}, urldate = {2021-09-19} } IISpy: A complex server‑side backdoor with anti‑forensic features
IISpy JuicyPotato
Yara Rules
[TLP:WHITE] win_iispy_auto (20220516 | Detects win.iispy.)
rule win_iispy_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2022-05-16"
        version = "1"
        description = "Detects win.iispy."
        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.iispy"
        malpedia_rule_date = "20220513"
        malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26"
        malpedia_version = "20220516"
        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 = { c745c400000000 68???????? 8d4da0 c745b000000000 0f1145a0 c745b400000000 c745b800000000 }
            // n = 7, score = 100
            //   c745c400000000       | mov                 dword ptr [ebp - 0x3c], 0
            //   68????????           |                     
            //   8d4da0               | lea                 ecx, [ebp - 0x60]
            //   c745b000000000       | mov                 dword ptr [ebp - 0x50], 0
            //   0f1145a0             | movups              xmmword ptr [ebp - 0x60], xmm0
            //   c745b400000000       | mov                 dword ptr [ebp - 0x4c], 0
            //   c745b800000000       | mov                 dword ptr [ebp - 0x48], 0

        $sequence_1 = { 894b1c 5f 5e 5b 8be5 5d c20800 }
            // n = 7, score = 100
            //   894b1c               | mov                 dword ptr [ebx + 0x1c], ecx
            //   5f                   | pop                 edi
            //   5e                   | pop                 esi
            //   5b                   | pop                 ebx
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp
            //   c20800               | ret                 8

        $sequence_2 = { 6b45e430 8945e0 8d8010c60210 8945e4 803800 }
            // n = 5, score = 100
            //   6b45e430             | imul                eax, dword ptr [ebp - 0x1c], 0x30
            //   8945e0               | mov                 dword ptr [ebp - 0x20], eax
            //   8d8010c60210         | lea                 eax, [eax + 0x1002c610]
            //   8945e4               | mov                 dword ptr [ebp - 0x1c], eax
            //   803800               | cmp                 byte ptr [eax], 0

        $sequence_3 = { c745dc00000000 0f1145c4 6a0a 68???????? e8???????? 8b45c0 c745fc03000000 }
            // n = 7, score = 100
            //   c745dc00000000       | mov                 dword ptr [ebp - 0x24], 0
            //   0f1145c4             | movups              xmmword ptr [ebp - 0x3c], xmm0
            //   6a0a                 | push                0xa
            //   68????????           |                     
            //   e8????????           |                     
            //   8b45c0               | mov                 eax, dword ptr [ebp - 0x40]
            //   c745fc03000000       | mov                 dword ptr [ebp - 4], 3

        $sequence_4 = { ff75d4 e8???????? 83c404 6a01 ff75cc e8???????? 83c408 }
            // n = 7, score = 100
            //   ff75d4               | push                dword ptr [ebp - 0x2c]
            //   e8????????           |                     
            //   83c404               | add                 esp, 4
            //   6a01                 | push                1
            //   ff75cc               | push                dword ptr [ebp - 0x34]
            //   e8????????           |                     
            //   83c408               | add                 esp, 8

        $sequence_5 = { 83e803 0f84e9000000 83e801 747c 83e801 7415 }
            // n = 6, score = 100
            //   83e803               | sub                 eax, 3
            //   0f84e9000000         | je                  0xef
            //   83e801               | sub                 eax, 1
            //   747c                 | je                  0x7e
            //   83e801               | sub                 eax, 1
            //   7415                 | je                  0x17

        $sequence_6 = { 85c0 c744241000000000 0f45c8 8d442410 51 }
            // n = 5, score = 100
            //   85c0                 | test                eax, eax
            //   c744241000000000     | mov                 dword ptr [esp + 0x10], 0
            //   0f45c8               | cmovne              ecx, eax
            //   8d442410             | lea                 eax, [esp + 0x10]
            //   51                   | push                ecx

        $sequence_7 = { f7d1 8bc2 234604 234e08 0bc8 660f7ec0 }
            // n = 6, score = 100
            //   f7d1                 | not                 ecx
            //   8bc2                 | mov                 eax, edx
            //   234604               | and                 eax, dword ptr [esi + 4]
            //   234e08               | and                 ecx, dword ptr [esi + 8]
            //   0bc8                 | or                  ecx, eax
            //   660f7ec0             | movd                eax, xmm0

        $sequence_8 = { 8bc1 8b4804 8bd1 8b700c f7d2 2310 8bc6 }
            // n = 7, score = 100
            //   8bc1                 | mov                 eax, ecx
            //   8b4804               | mov                 ecx, dword ptr [eax + 4]
            //   8bd1                 | mov                 edx, ecx
            //   8b700c               | mov                 esi, dword ptr [eax + 0xc]
            //   f7d2                 | not                 edx
            //   2310                 | and                 edx, dword ptr [eax]
            //   8bc6                 | mov                 eax, esi

        $sequence_9 = { e8???????? c745fc03000000 8b4618 51 8d4da0 ff7010 50 }
            // n = 7, score = 100
            //   e8????????           |                     
            //   c745fc03000000       | mov                 dword ptr [ebp - 4], 3
            //   8b4618               | mov                 eax, dword ptr [esi + 0x18]
            //   51                   | push                ecx
            //   8d4da0               | lea                 ecx, [ebp - 0x60]
            //   ff7010               | push                dword ptr [eax + 0x10]
            //   50                   | push                eax

    condition:
        7 of them and filesize < 397312
}
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