SYMBOLCOMMON_NAMEaka. SYNONYMS
win.netrepser_keylogger (Back to overview)

Netrepser


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References
2017-05-05BitdefenderBogdan Botezatu, Alexandru Maximciuc, Cristina Vatamanu, Adrian Schipur
@online{botezatu:20170505:inside:0cff0e6, author = {Bogdan Botezatu and Alexandru Maximciuc and Cristina Vatamanu and Adrian Schipur}, title = {{Inside Netrepser – a JavaScript-based Targeted Attack}}, date = {2017-05-05}, organization = {Bitdefender}, url = {https://labs.bitdefender.com/2017/05/inside-netrepser-a-javascript-based-targeted-attack/}, language = {English}, urldate = {2020-01-08} } Inside Netrepser – a JavaScript-based Targeted Attack
Netrepser
Yara Rules
[TLP:WHITE] win_netrepser_keylogger_auto (20230715 | Detects win.netrepser_keylogger.)
rule win_netrepser_keylogger_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-07-11"
        version = "1"
        description = "Detects win.netrepser_keylogger."
        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.netrepser_keylogger"
        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 = { 8d45f8 50 8d4dec 51 e8???????? 83c404 }
            // n = 6, score = 200
            //   8d45f8               | lea                 eax, [ebp - 8]
            //   50                   | push                eax
            //   8d4dec               | lea                 ecx, [ebp - 0x14]
            //   51                   | push                ecx
            //   e8????????           |                     
            //   83c404               | add                 esp, 4

        $sequence_1 = { 50 e8???????? 83c40c c785dcfcffffe0000000 c745f800000000 c745fc00000000 c745f000000000 }
            // n = 7, score = 200
            //   50                   | push                eax
            //   e8????????           |                     
            //   83c40c               | add                 esp, 0xc
            //   c785dcfcffffe0000000     | mov    dword ptr [ebp - 0x324], 0xe0
            //   c745f800000000       | mov                 dword ptr [ebp - 8], 0
            //   c745fc00000000       | mov                 dword ptr [ebp - 4], 0
            //   c745f000000000       | mov                 dword ptr [ebp - 0x10], 0

        $sequence_2 = { c645f200 c645f447 c645f565 c645f674 c645f74b c645f865 }
            // n = 6, score = 200
            //   c645f200             | mov                 byte ptr [ebp - 0xe], 0
            //   c645f447             | mov                 byte ptr [ebp - 0xc], 0x47
            //   c645f565             | mov                 byte ptr [ebp - 0xb], 0x65
            //   c645f674             | mov                 byte ptr [ebp - 0xa], 0x74
            //   c645f74b             | mov                 byte ptr [ebp - 9], 0x4b
            //   c645f865             | mov                 byte ptr [ebp - 8], 0x65

        $sequence_3 = { c7859ce4ffff56657273 c785a0e4ffff696f6e5c c785a4e4ffff52756e5d c785a8e4ffff203e3e20 }
            // n = 4, score = 200
            //   c7859ce4ffff56657273     | mov    dword ptr [ebp - 0x1b64], 0x73726556
            //   c785a0e4ffff696f6e5c     | mov    dword ptr [ebp - 0x1b60], 0x5c6e6f69
            //   c785a4e4ffff52756e5d     | mov    dword ptr [ebp - 0x1b5c], 0x5d6e7552
            //   c785a8e4ffff203e3e20     | mov    dword ptr [ebp - 0x1b58], 0x203e3e20

        $sequence_4 = { 0355f8 0fb602 c1f804 0fbe4df3 }
            // n = 4, score = 200
            //   0355f8               | add                 edx, dword ptr [ebp - 8]
            //   0fb602               | movzx               eax, byte ptr [edx]
            //   c1f804               | sar                 eax, 4
            //   0fbe4df3             | movsx               ecx, byte ptr [ebp - 0xd]

        $sequence_5 = { 6a00 8d8df0feffff 51 e8???????? 68f4010000 ff15???????? }
            // n = 6, score = 200
            //   6a00                 | push                0
            //   8d8df0feffff         | lea                 ecx, [ebp - 0x110]
            //   51                   | push                ecx
            //   e8????????           |                     
            //   68f4010000           | push                0x1f4
            //   ff15????????         |                     

        $sequence_6 = { 8d148501000000 52 e8???????? 83c404 8945f4 837df400 }
            // n = 6, score = 200
            //   8d148501000000       | lea                 edx, [eax*4 + 1]
            //   52                   | push                edx
            //   e8????????           |                     
            //   83c404               | add                 esp, 4
            //   8945f4               | mov                 dword ptr [ebp - 0xc], eax
            //   837df400             | cmp                 dword ptr [ebp - 0xc], 0

        $sequence_7 = { b801000000 eb27 8d85b0fdffff 50 }
            // n = 4, score = 200
            //   b801000000           | mov                 eax, 1
            //   eb27                 | jmp                 0x29
            //   8d85b0fdffff         | lea                 eax, [ebp - 0x250]
            //   50                   | push                eax

        $sequence_8 = { 895c2410 89742414 eb18 c744240877696e68 }
            // n = 4, score = 100
            //   895c2410             | mov                 dword ptr [esp + 0x10], ebx
            //   89742414             | mov                 dword ptr [esp + 0x14], esi
            //   eb18                 | jmp                 0x1a
            //   c744240877696e68     | mov                 dword ptr [esp + 8], 0x686e6977

        $sequence_9 = { 6a0a 53 56 ffd0 }
            // n = 4, score = 100
            //   6a0a                 | push                0xa
            //   53                   | push                ebx
            //   56                   | push                esi
            //   ffd0                 | call                eax

        $sequence_10 = { 89442410 89442414 8d442410 50 8d4c2418 51 }
            // n = 6, score = 100
            //   89442410             | mov                 dword ptr [esp + 0x10], eax
            //   89442414             | mov                 dword ptr [esp + 0x14], eax
            //   8d442410             | lea                 eax, [esp + 0x10]
            //   50                   | push                eax
            //   8d4c2418             | lea                 ecx, [esp + 0x18]
            //   51                   | push                ecx

        $sequence_11 = { 8bf8 3bfe 0f84ca010000 68???????? 57 }
            // n = 5, score = 100
            //   8bf8                 | mov                 edi, eax
            //   3bfe                 | cmp                 edi, esi
            //   0f84ca010000         | je                  0x1d0
            //   68????????           |                     
            //   57                   | push                edi

        $sequence_12 = { 7561 a1???????? 3bc6 7528 8d442408 }
            // n = 5, score = 100
            //   7561                 | jne                 0x63
            //   a1????????           |                     
            //   3bc6                 | cmp                 eax, esi
            //   7528                 | jne                 0x2a
            //   8d442408             | lea                 eax, [esp + 8]

        $sequence_13 = { 85f6 7465 8d5518 52 }
            // n = 4, score = 100
            //   85f6                 | test                esi, esi
            //   7465                 | je                  0x67
            //   8d5518               | lea                 edx, [ebp + 0x18]
            //   52                   | push                edx

        $sequence_14 = { 81ec9c000000 a1???????? 33c4 89842498000000 8b8424a8000000 53 6890000000 }
            // n = 7, score = 100
            //   81ec9c000000         | sub                 esp, 0x9c
            //   a1????????           |                     
            //   33c4                 | xor                 eax, esp
            //   89842498000000       | mov                 dword ptr [esp + 0x98], eax
            //   8b8424a8000000       | mov                 eax, dword ptr [esp + 0xa8]
            //   53                   | push                ebx
            //   6890000000           | push                0x90

        $sequence_15 = { bd01000000 e8???????? 8bf0 85f6 0f849a000000 57 68???????? }
            // n = 7, score = 100
            //   bd01000000           | mov                 ebp, 1
            //   e8????????           |                     
            //   8bf0                 | mov                 esi, eax
            //   85f6                 | test                esi, esi
            //   0f849a000000         | je                  0xa0
            //   57                   | push                edi
            //   68????????           |                     

    condition:
        7 of them and filesize < 303104
}
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