SYMBOLCOMMON_NAMEaka. SYNONYMS
win.stegoloader (Back to overview)

StegoLoader


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References
2015-06-15SecureworksCTU Research Team
@online{team:20150615:stegoloader:9a04145, author = {CTU Research Team}, title = {{Stegoloader: A Stealthy Information Stealer}}, date = {2015-06-15}, organization = {Secureworks}, url = {https://www.secureworks.com/research/stegoloader-a-stealthy-information-stealer}, language = {English}, urldate = {2020-01-10} } Stegoloader: A Stealthy Information Stealer
StegoLoader
Yara Rules
[TLP:WHITE] win_stegoloader_auto (20201023 | autogenerated rule brought to you by yara-signator)
rule win_stegoloader_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2020-12-22"
        version = "1"
        description = "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.stegoloader"
        malpedia_rule_date = "20201222"
        malpedia_hash = "30354d830a29f0fbd3714d93d94dea941d77a130"
        malpedia_version = "20201023"
        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 = { 3b4508 59 59 7422 43 }
            // n = 5, score = 200
            //   3b4508               | cmp                 eax, dword ptr [ebp + 8]
            //   59                   | pop                 ecx
            //   59                   | pop                 ecx
            //   7422                 | je                  0x24
            //   43                   | inc                 ebx

        $sequence_1 = { ff15???????? 85c0 747d 8d85f8feffff 50 53 8d45fc }
            // n = 7, score = 200
            //   ff15????????         |                     
            //   85c0                 | test                eax, eax
            //   747d                 | je                  0x7f
            //   8d85f8feffff         | lea                 eax, [ebp - 0x108]
            //   50                   | push                eax
            //   53                   | push                ebx
            //   8d45fc               | lea                 eax, [ebp - 4]

        $sequence_2 = { 894dfc 895514 fe8000010000 0fb68800010000 }
            // n = 4, score = 200
            //   894dfc               | mov                 dword ptr [ebp - 4], ecx
            //   895514               | mov                 dword ptr [ebp + 0x14], edx
            //   fe8000010000         | inc                 byte ptr [eax + 0x100]
            //   0fb68800010000       | movzx               ecx, byte ptr [eax + 0x100]

        $sequence_3 = { 8908 0fb74d48 885808 894804 }
            // n = 4, score = 200
            //   8908                 | mov                 dword ptr [eax], ecx
            //   0fb74d48             | movzx               ecx, word ptr [ebp + 0x48]
            //   885808               | mov                 byte ptr [eax + 8], bl
            //   894804               | mov                 dword ptr [eax + 4], ecx

        $sequence_4 = { 0d00000080 8945f4 8b45f4 5e 5b }
            // n = 5, score = 200
            //   0d00000080           | or                  eax, 0x80000000
            //   8945f4               | mov                 dword ptr [ebp - 0xc], eax
            //   8b45f4               | mov                 eax, dword ptr [ebp - 0xc]
            //   5e                   | pop                 esi
            //   5b                   | pop                 ebx

        $sequence_5 = { e8???????? 84c0 7409 e8???????? 84c0 75ec 8bce }
            // n = 7, score = 200
            //   e8????????           |                     
            //   84c0                 | test                al, al
            //   7409                 | je                  0xb
            //   e8????????           |                     
            //   84c0                 | test                al, al
            //   75ec                 | jne                 0xffffffee
            //   8bce                 | mov                 ecx, esi

        $sequence_6 = { c745f45c163967 33f6 46 3bfe }
            // n = 4, score = 200
            //   c745f45c163967       | mov                 dword ptr [ebp - 0xc], 0x6739165c
            //   33f6                 | xor                 esi, esi
            //   46                   | inc                 esi
            //   3bfe                 | cmp                 edi, esi

        $sequence_7 = { 83c40c c3 55 8d6c248c 81ecc0000000 53 8d45b4 }
            // n = 7, score = 200
            //   83c40c               | add                 esp, 0xc
            //   c3                   | ret                 
            //   55                   | push                ebp
            //   8d6c248c             | lea                 ebp, [esp - 0x74]
            //   81ecc0000000         | sub                 esp, 0xc0
            //   53                   | push                ebx
            //   8d45b4               | lea                 eax, [ebp - 0x4c]

        $sequence_8 = { c645e36c c645e42c c645e543 c645e66f c645e76e c645e874 }
            // n = 6, score = 200
            //   c645e36c             | mov                 byte ptr [ebp - 0x1d], 0x6c
            //   c645e42c             | mov                 byte ptr [ebp - 0x1c], 0x2c
            //   c645e543             | mov                 byte ptr [ebp - 0x1b], 0x43
            //   c645e66f             | mov                 byte ptr [ebp - 0x1a], 0x6f
            //   c645e76e             | mov                 byte ptr [ebp - 0x19], 0x6e
            //   c645e874             | mov                 byte ptr [ebp - 0x18], 0x74

        $sequence_9 = { 57 e8???????? 8bf8 68eb2f76e0 e8???????? 685eced6e9 8945e8 }
            // n = 7, score = 200
            //   57                   | push                edi
            //   e8????????           |                     
            //   8bf8                 | mov                 edi, eax
            //   68eb2f76e0           | push                0xe0762feb
            //   e8????????           |                     
            //   685eced6e9           | push                0xe9d6ce5e
            //   8945e8               | mov                 dword ptr [ebp - 0x18], eax

        $sequence_10 = { 33d2 c645ff00 8bc8 8bc7 }
            // n = 4, score = 200
            //   33d2                 | xor                 edx, edx
            //   c645ff00             | mov                 byte ptr [ebp - 1], 0
            //   8bc8                 | mov                 ecx, eax
            //   8bc7                 | mov                 eax, edi

        $sequence_11 = { 8a043e 0fb6d8 46 8d043e 50 }
            // n = 5, score = 200
            //   8a043e               | mov                 al, byte ptr [esi + edi]
            //   0fb6d8               | movzx               ebx, al
            //   46                   | inc                 esi
            //   8d043e               | lea                 eax, [esi + edi]
            //   50                   | push                eax

        $sequence_12 = { 64a130000000 8945fc 8b45fc 8b400c 8b400c 53 }
            // n = 6, score = 200
            //   64a130000000         | mov                 eax, dword ptr fs:[0x30]
            //   8945fc               | mov                 dword ptr [ebp - 4], eax
            //   8b45fc               | mov                 eax, dword ptr [ebp - 4]
            //   8b400c               | mov                 eax, dword ptr [eax + 0xc]
            //   8b400c               | mov                 eax, dword ptr [eax + 0xc]
            //   53                   | push                ebx

        $sequence_13 = { 2bc3 5e 8be5 5d }
            // n = 4, score = 200
            //   2bc3                 | sub                 eax, ebx
            //   5e                   | pop                 esi
            //   8be5                 | mov                 esp, ebp
            //   5d                   | pop                 ebp

        $sequence_14 = { 75e9 eb5b 83e803 eb02 48 }
            // n = 5, score = 200
            //   75e9                 | jne                 0xffffffeb
            //   eb5b                 | jmp                 0x5d
            //   83e803               | sub                 eax, 3
            //   eb02                 | jmp                 4
            //   48                   | dec                 eax

        $sequence_15 = { eb07 662b5e10 0fb7c3 8b4e1c 0fb7c0 }
            // n = 5, score = 200
            //   eb07                 | jmp                 9
            //   662b5e10             | sub                 bx, word ptr [esi + 0x10]
            //   0fb7c3               | movzx               eax, bx
            //   8b4e1c               | mov                 ecx, dword ptr [esi + 0x1c]
            //   0fb7c0               | movzx               eax, ax

    condition:
        7 of them and filesize < 802816
}
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