SYMBOLCOMMON_NAMEaka. SYNONYMS
win.oski (Back to overview)

Oski Stealer


Oski is a stealer written in C++ that appeared around November 2019 and is being sold for between 70$ to 100$ on Russian-speaking forums. It collects different types of data (cryptocurrency wallets, saved passwords, files matching an attacker-defined pattern etc) and it exfiltrates it in a zip file uploaded to the attacker's panel.

References
2021-11-02MinervaNatalie Zargarov
@online{zargarov:20211102:underminer:f03f426, author = {Natalie Zargarov}, title = {{Underminer Exploit Kit: The More You Check The More Evasive You Become}}, date = {2021-11-02}, organization = {Minerva}, url = {https://blog.minerva-labs.com/underminer-exploit-kit-the-more-you-check-the-more-evasive-you-become}, language = {English}, urldate = {2021-11-03} } Underminer Exploit Kit: The More You Check The More Evasive You Become
Amadey Oski Stealer RedLine Stealer UnderminerEK
2021-07-27ZAYOTEMİlker Verimoğlu
@online{verimolu:20210727:oski:8afb3fb, author = {İlker Verimoğlu}, title = {{Oski Stealer Technical Analysis Report}}, date = {2021-07-27}, organization = {ZAYOTEM}, url = {https://drive.google.com/file/d/1c72YIF6JYcEvbFZCrkZO26D9hC3gnyMP/view}, language = {English}, urldate = {2021-08-17} } Oski Stealer Technical Analysis Report
Oski Stealer
2021-06-29YoroiLuigi Martire, Luca Mella
@online{martire:20210629:wayback:fc8fa84, author = {Luigi Martire and Luca Mella}, title = {{The "WayBack” Campaign: a Large Scale Operation Hiding in Plain Sight}}, date = {2021-06-29}, organization = {Yoroi}, url = {https://yoroi.company/research/the-wayback-campaign-a-large-scale-operation-hiding-in-plain-sight/}, language = {English}, urldate = {2021-06-29} } The "WayBack” Campaign: a Large Scale Operation Hiding in Plain Sight
Agent Tesla Cobian RAT Oski Stealer
2021-01-16MediumIsha Kudkar
@online{kudkar:20210116:oski:a0abdb1, author = {Isha Kudkar}, title = {{Oski Stealer : A Credential Theft Malware}}, date = {2021-01-16}, organization = {Medium}, url = {https://medium.com/shallvhack/oski-stealer-a-credential-theft-malware-b9bba5164601}, language = {English}, urldate = {2022-01-12} } Oski Stealer : A Credential Theft Malware
Oski Stealer
2021-01-07CyberArkBen Cohen
@online{cohen:20210107:meet:9fbcca8, author = {Ben Cohen}, title = {{Meet Oski Stealer: An In-depth Analysis of the Popular Credential Stealer}}, date = {2021-01-07}, organization = {CyberArk}, url = {https://www.cyberark.com/resources/threat-research-blog/meet-oski-stealer-an-in-depth-analysis-of-the-popular-credential-stealer}, language = {English}, urldate = {2021-01-11} } Meet Oski Stealer: An In-depth Analysis of the Popular Credential Stealer
Oski Stealer
2020-03-25BitdefenderLiviu Arsene
@online{arsene:20200325:new:51ce027, author = {Liviu Arsene}, title = {{New Router DNS Hijacking Attacks Abuse Bitbucket to Host Infostealer}}, date = {2020-03-25}, organization = {Bitdefender}, url = {https://labs.bitdefender.com/2020/03/new-router-dns-hijacking-attacks-abuse-bitbucket-to-host-infostealer/}, language = {English}, urldate = {2020-03-30} } New Router DNS Hijacking Attacks Abuse Bitbucket to Host Infostealer
Oski Stealer
2019-08-12Twitter (@albertzsigovits)Albert Zsigovits
@online{zsigovits:20190812:oski:699b3d0, author = {Albert Zsigovits}, title = {{Tweet on Oski Stealer}}, date = {2019-08-12}, organization = {Twitter (@albertzsigovits)}, url = {https://twitter.com/albertzsigovits/status/1160874557454131200}, language = {English}, urldate = {2020-03-19} } Tweet on Oski Stealer
Oski Stealer
Yara Rules
[TLP:WHITE] win_oski_auto (20211008 | Detects win.oski.)
rule win_oski_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2021-10-07"
        version = "1"
        description = "Detects win.oski."
        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.oski"
        malpedia_rule_date = "20211007"
        malpedia_hash = "e5b790e0f888f252d49063a1251ca60ec2832535"
        malpedia_version = "20211008"
        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 = { 83c120 51 6a00 6a00 }
            // n = 4, score = 900
            //   83c120               | add                 ecx, 0x20
            //   51                   | push                ecx
            //   6a00                 | push                0
            //   6a00                 | push                0

        $sequence_1 = { 25ff7f0000 c3 8bff 55 8bec 83ec14 ff7510 }
            // n = 7, score = 900
            //   25ff7f0000           | and                 eax, 0x7fff
            //   c3                   | ret                 
            //   8bff                 | mov                 edi, edi
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   83ec14               | sub                 esp, 0x14
            //   ff7510               | push                dword ptr [ebp + 0x10]

        $sequence_2 = { a1???????? 50 8d8df0feffff 51 }
            // n = 4, score = 800
            //   a1????????           |                     
            //   50                   | push                eax
            //   8d8df0feffff         | lea                 ecx, dword ptr [ebp - 0x110]
            //   51                   | push                ecx

        $sequence_3 = { 83c40c e8???????? 50 a1???????? }
            // n = 4, score = 800
            //   83c40c               | add                 esp, 0xc
            //   e8????????           |                     
            //   50                   | push                eax
            //   a1????????           |                     

        $sequence_4 = { 8975f0 e8???????? cc 8bff 55 8bec 8b550c }
            // n = 7, score = 800
            //   8975f0               | mov                 dword ptr [ebp - 0x10], esi
            //   e8????????           |                     
            //   cc                   | int3                
            //   8bff                 | mov                 edi, edi
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   8b550c               | mov                 edx, dword ptr [ebp + 0xc]

        $sequence_5 = { 895dac 85db 7466 837de810 8b45d4 7303 }
            // n = 6, score = 700
            //   895dac               | mov                 dword ptr [ebp - 0x54], ebx
            //   85db                 | test                ebx, ebx
            //   7466                 | je                  0x68
            //   837de810             | cmp                 dword ptr [ebp - 0x18], 0x10
            //   8b45d4               | mov                 eax, dword ptr [ebp - 0x2c]
            //   7303                 | jae                 5

        $sequence_6 = { 89bdecfbffff 89bdf4fbffff ff15???????? 8bd8 }
            // n = 4, score = 700
            //   89bdecfbffff         | mov                 dword ptr [ebp - 0x414], edi
            //   89bdf4fbffff         | mov                 dword ptr [ebp - 0x40c], edi
            //   ff15????????         |                     
            //   8bd8                 | mov                 ebx, eax

        $sequence_7 = { 7502 f3c3 e9???????? 8bff 55 8bec 83ec1c }
            // n = 7, score = 700
            //   7502                 | jne                 4
            //   f3c3                 | ret                 
            //   e9????????           |                     
            //   8bff                 | mov                 edi, edi
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   83ec1c               | sub                 esp, 0x1c

        $sequence_8 = { e8???????? 8b55ac 8b75b0 6803010000 52 }
            // n = 5, score = 700
            //   e8????????           |                     
            //   8b55ac               | mov                 edx, dword ptr [ebp - 0x54]
            //   8b75b0               | mov                 esi, dword ptr [ebp - 0x50]
            //   6803010000           | push                0x103
            //   52                   | push                edx

        $sequence_9 = { 52 6804010000 ff15???????? 6a00 }
            // n = 4, score = 300
            //   52                   | push                edx
            //   6804010000           | push                0x104
            //   ff15????????         |                     
            //   6a00                 | push                0

        $sequence_10 = { 8b4dfc 8b510c 52 a1???????? }
            // n = 4, score = 200
            //   8b4dfc               | mov                 ecx, dword ptr [ebp - 4]
            //   8b510c               | mov                 edx, dword ptr [ecx + 0xc]
            //   52                   | push                edx
            //   a1????????           |                     

        $sequence_11 = { 8b4d08 8b55d8 89948104100000 8b45d8 8945e0 }
            // n = 5, score = 200
            //   8b4d08               | mov                 ecx, dword ptr [ebp + 8]
            //   8b55d8               | mov                 edx, dword ptr [ebp - 0x28]
            //   89948104100000       | mov                 dword ptr [ecx + eax*4 + 0x1004], edx
            //   8b45d8               | mov                 eax, dword ptr [ebp - 0x28]
            //   8945e0               | mov                 dword ptr [ebp - 0x20], eax

        $sequence_12 = { 7425 8b95f4f7ffff 52 ff15???????? 8b85f0f7ffff }
            // n = 5, score = 200
            //   7425                 | je                  0x27
            //   8b95f4f7ffff         | mov                 edx, dword ptr [ebp - 0x80c]
            //   52                   | push                edx
            //   ff15????????         |                     
            //   8b85f0f7ffff         | mov                 eax, dword ptr [ebp - 0x810]

    condition:
        7 of them and filesize < 423936
}
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