SYMBOLCOMMON_NAMEaka. SYNONYMS
win.ryuk_stealer (Back to overview)

Ryuk Stealer

aka: Sidoh

Information Stealer that searches for sensitive documents and uploads its results to an FTP server. Skips files with known Ryuk extensions.

References
2021-08-31CrowdStrikeAlexander Hanel
@online{hanel:20210831:sidoh:8a5c018, author = {Alexander Hanel}, title = {{Sidoh: WIZARD SPIDER’s Mysterious Exfiltration Tool}}, date = {2021-08-31}, organization = {CrowdStrike}, url = {https://www.crowdstrike.com/blog/sidoh-wizard-spiders-mysterious-exfiltration-tool/}, language = {English}, urldate = {2021-09-02} } Sidoh: WIZARD SPIDER’s Mysterious Exfiltration Tool
Ryuk Stealer
2021-08-11ANALYST1Jon DiMaggio
@techreport{dimaggio:20210811:nation:815fed9, author = {Jon DiMaggio}, title = {{Nation State Ransomware}}, date = {2021-08-11}, institution = {ANALYST1}, url = {https://analyst1.com/file-assets/Nationstate_ransomware_with_consecutive_endnotes.pdf}, language = {English}, urldate = {2021-08-17} } Nation State Ransomware
Ryuk Stealer
2019-09-11Twitter (@VK_intel)Vitali Kremez
@online{kremez:20190911:stealeruploader:0d4c48f, author = {Vitali Kremez}, title = {{Tweet on Stealer/Uploader}}, date = {2019-09-11}, organization = {Twitter (@VK_intel)}, url = {https://twitter.com/VK_Intel/status/1171782155581689858}, language = {English}, urldate = {2020-01-07} } Tweet on Stealer/Uploader
Ryuk Stealer
2019-09-11Bleeping ComputerLawrence Abrams
@online{abrams:20190911:ryuk:8a18715, author = {Lawrence Abrams}, title = {{Ryuk Related Malware Steals Confidential Military, Financial Files}}, date = {2019-09-11}, organization = {Bleeping Computer}, url = {https://www.bleepingcomputer.com/news/security/ryuk-related-malware-steals-confidential-military-financial-files/}, language = {English}, urldate = {2019-12-20} } Ryuk Related Malware Steals Confidential Military, Financial Files
Ryuk Stealer
Yara Rules
[TLP:WHITE] win_ryuk_stealer_auto (20230125 | Detects win.ryuk_stealer.)
rule win_ryuk_stealer_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2023-01-25"
        version = "1"
        description = "Detects win.ryuk_stealer."
        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.ryuk_stealer"
        malpedia_rule_date = "20230124"
        malpedia_hash = "2ee0eebba83dce3d019a90519f2f972c0fcf9686"
        malpedia_version = "20230125"
        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 = { 6bc064 05???????? 50 8d85b4fdffff }
            // n = 4, score = 800
            //   6bc064               | imul                eax, eax, 0x64
            //   05????????           |                     
            //   50                   | push                eax
            //   8d85b4fdffff         | lea                 eax, [ebp - 0x24c]

        $sequence_1 = { 8d85b4fdffff 6a2e 50 e8???????? }
            // n = 4, score = 800
            //   8d85b4fdffff         | lea                 eax, [ebp - 0x24c]
            //   6a2e                 | push                0x2e
            //   50                   | push                eax
            //   e8????????           |                     

        $sequence_2 = { 8bc8 33d2 8bc6 f7f1 6a0a }
            // n = 5, score = 800
            //   8bc8                 | mov                 ecx, eax
            //   33d2                 | xor                 edx, edx
            //   8bc6                 | mov                 eax, esi
            //   f7f1                 | div                 ecx
            //   6a0a                 | push                0xa

        $sequence_3 = { 8a443706 3c2f 7404 3c2d }
            // n = 4, score = 800
            //   8a443706             | mov                 al, byte ptr [edi + esi + 6]
            //   3c2f                 | cmp                 al, 0x2f
            //   7404                 | je                  6
            //   3c2d                 | cmp                 al, 0x2d

        $sequence_4 = { b910270000 f7f1 8bf2 e8???????? 8bc8 33d2 8bc6 }
            // n = 7, score = 800
            //   b910270000           | mov                 ecx, 0x2710
            //   f7f1                 | div                 ecx
            //   8bf2                 | mov                 esi, edx
            //   e8????????           |                     
            //   8bc8                 | mov                 ecx, eax
            //   33d2                 | xor                 edx, edx
            //   8bc6                 | mov                 eax, esi

        $sequence_5 = { 99 b9a0860100 f7f9 81c2a8610000 52 }
            // n = 5, score = 800
            //   99                   | cdq                 
            //   b9a0860100           | mov                 ecx, 0x186a0
            //   f7f9                 | idiv                ecx
            //   81c2a8610000         | add                 edx, 0x61a8
            //   52                   | push                edx

        $sequence_6 = { ff15???????? 83f805 740a b9???????? }
            // n = 4, score = 800
            //   ff15????????         |                     
            //   83f805               | cmp                 eax, 5
            //   740a                 | je                  0xc
            //   b9????????           |                     

        $sequence_7 = { f7f9 81c2a8610000 52 ff15???????? }
            // n = 4, score = 800
            //   f7f9                 | idiv                ecx
            //   81c2a8610000         | add                 edx, 0x61a8
            //   52                   | push                edx
            //   ff15????????         |                     

        $sequence_8 = { ff15???????? 33ff 0fb60437 50 }
            // n = 4, score = 800
            //   ff15????????         |                     
            //   33ff                 | xor                 edi, edi
            //   0fb60437             | movzx               eax, byte ptr [edi + esi]
            //   50                   | push                eax

        $sequence_9 = { 83f801 7410 83ff01 755d }
            // n = 4, score = 800
            //   83f801               | cmp                 eax, 1
            //   7410                 | je                  0x12
            //   83ff01               | cmp                 edi, 1
            //   755d                 | jne                 0x5f

    condition:
        7 of them and filesize < 368640
}
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