win.kerrdown (Back to overview)

KerrDown

Actor(s): APT32

URLhaus    

There is no description at this point.

References
https://unit42.paloaltonetworks.com/tracking-oceanlotus-new-downloader-kerrdown/
https://blog.cystack.net/word-based-malware-attack/
Yara Rules
[TLP:WHITE] win_kerrdown_auto (20190620 | autogenerated rule brought to you by yara-signator)
rule win_kerrdown_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2019-07-05"
        version = "1"
        description = "autogenerated rule brought to you by yara-signator"
        tool = "yara-signator 0.2a"
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.kerrdown"
        malpedia_version = "20190620"
        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 / approach 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 = { 6a00 ff15???????? 8b4dfc b801000000 5e }
            // n = 5, score = 200
            //   6a00                 | push                0
            //   ff15????????         |                     
            //   8b4dfc               | mov                 ecx, dword ptr [ebp - 4]
            //   b801000000           | mov                 eax, 1
            //   5e                   | pop                 esi

        $sequence_1 = { 50 e8???????? 8b3d???????? 83c40c 8b0d???????? 83ff10 }
            // n = 6, score = 200
            //   50                   | push                eax
            //   e8????????           |                     
            //   8b3d????????         |                     
            //   83c40c               | add                 esp, 0xc
            //   8b0d????????         |                     
            //   83ff10               | cmp                 edi, 0x10

        $sequence_2 = { 837d1c10 8d4d08 ff7518 0f434d08 }
            // n = 4, score = 200
            //   837d1c10             | cmp                 dword ptr [ebp + 0x1c], 0x10
            //   8d4d08               | lea                 ecx, [ebp + 8]
            //   ff7518               | push                dword ptr [ebp + 0x18]
            //   0f434d08             | cmovae              ecx, dword ptr [ebp + 8]

        $sequence_3 = { 8bf0 e8???????? 8bd8 83c408 8bd3 2bd6 8a0e }
            // n = 7, score = 200
            //   8bf0                 | mov                 esi, eax
            //   e8????????           |                     
            //   8bd8                 | mov                 ebx, eax
            //   83c408               | add                 esp, 8
            //   8bd3                 | mov                 edx, ebx
            //   2bd6                 | sub                 edx, esi
            //   8a0e                 | mov                 cl, byte ptr [esi]

        $sequence_4 = { 33db 8a55ea 8aca c0e206 c0e902 80e10f }
            // n = 6, score = 200
            //   33db                 | xor                 ebx, ebx
            //   8a55ea               | mov                 dl, byte ptr [ebp - 0x16]
            //   8aca                 | mov                 cl, dl
            //   c0e206               | shl                 dl, 6
            //   c0e902               | shr                 cl, 2
            //   80e10f               | and                 cl, 0xf

        $sequence_5 = { 6807800000 ff15???????? e8???????? 8d4c2404 e8???????? 83ec18 }
            // n = 6, score = 200
            //   6807800000           | push                0x8007
            //   ff15????????         |                     
            //   e8????????           |                     
            //   8d4c2404             | lea                 ecx, [esp + 4]
            //   e8????????           |                     
            //   83ec18               | sub                 esp, 0x18

        $sequence_6 = { c741140f000000 c7411000000000 50 c60100 e8???????? e8???????? 8b442430 }
            // n = 7, score = 200
            //   c741140f000000       | mov                 dword ptr [ecx + 0x14], 0xf
            //   c7411000000000       | mov                 dword ptr [ecx + 0x10], 0
            //   50                   | push                eax
            //   c60100               | mov                 byte ptr [ecx], 0
            //   e8????????           |                     
            //   e8????????           |                     
            //   8b442430             | mov                 eax, dword ptr [esp + 0x30]

        $sequence_7 = { 02c2 33f6 8845e6 0fb64435e4 }
            // n = 4, score = 200
            //   02c2                 | add                 al, dl
            //   33f6                 | xor                 esi, esi
            //   8845e6               | mov                 byte ptr [ebp - 0x1a], al
            //   0fb64435e4           | movzx               eax, byte ptr [ebp + esi - 0x1c]

    condition:
        7 of them
}
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