FatalRat (Malware Family)

FatalRat

aka: Sainbox RAT

VTCollection

FatalRAT is a most-likely chinese remote access tool distributed through forums and Telegram channels. FatalRAT executes various anti-virtual machine tests to avoid detection before fully infecting systems. Upon successful infiltration, it decrypts configuration strings, disables the CTRL+ALT+DELETE function, and activates a keylogger.

The malware can establish persistence via registry modifications or service creation, collect sensitive data, and communicate with its command and control (C&C) server using encrypted methods. FatalRAT also employs techniques like brute-force attacks against weak passwords to propagate within networks.

References

2023-09-20 ⋅ Proofpoint ⋅ Proofpoint Threat Research Team
Chinese Malware Appears in Earnest Across Cybercrime Threat Landscape
FatalRat PurpleFox ValleyRAT

2022-03-28 ⋅ The Hacker News ⋅ Ravie Lakshmanan
'Purple Fox' Hackers Spotted Using New Variant of FatalRAT in Recent Malware Attacks
DirtyMoe FatalRat PurpleFox

2022-03-25 ⋅ Trend Micro ⋅ Abdelrhman Sharshar, Jay Yaneza, Sherif Magdy
Purple Fox Uses New Arrival Vector and Improves Malware Arsenal
FatalRat PurpleFox

2021-08-02 ⋅ AT&T ⋅ Javier Ruiz, Ofer Caspi
New sophisticated RAT in town: FatalRat analysis
FatalRat

2021-06-03 ⋅ YouTube (0xca7) ⋅ 0xca7
FatalRAT: Dumping the "payload" aka. Cat vs RAT
FatalRat

Yara Rules

[TLP:WHITE] win_fatal_rat_auto (20241030 | Detects win.fatal_rat.)

rule win_fatal_rat_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2024-10-31"
        version = "1"
        description = "Detects win.fatal_rat."
        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.fatal_rat"
        malpedia_rule_date = "20241030"
        malpedia_hash = "26e26953c49c8efafbf72a38076855d578e0a2e4"
        malpedia_version = "20241030"
        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 = { 57 ff15???????? 3bc7 89450c 0f8415020000 8d4b02 56 }
            // n = 7, score = 100
            //   57                   | push                edi
            //   ff15????????         |                     
            //   3bc7                 | cmp                 eax, edi
            //   89450c               | mov                 dword ptr [ebp + 0xc], eax
            //   0f8415020000         | je                  0x21b
            //   8d4b02               | lea                 ecx, [ebx + 2]
            //   56                   | push                esi

        $sequence_1 = { c6458265 c6458378 c6458465 885d85 c645a065 c645a167 c645a275 }
            // n = 7, score = 100
            //   c6458265             | mov                 byte ptr [ebp - 0x7e], 0x65
            //   c6458378             | mov                 byte ptr [ebp - 0x7d], 0x78
            //   c6458465             | mov                 byte ptr [ebp - 0x7c], 0x65
            //   885d85               | mov                 byte ptr [ebp - 0x7b], bl
            //   c645a065             | mov                 byte ptr [ebp - 0x60], 0x65
            //   c645a167             | mov                 byte ptr [ebp - 0x5f], 0x67
            //   c645a275             | mov                 byte ptr [ebp - 0x5e], 0x75

        $sequence_2 = { 5f 5d c3 55 8bec 81ece0060000 53 }
            // n = 7, score = 100
            //   5f                   | pop                 edi
            //   5d                   | pop                 ebp
            //   c3                   | ret                 
            //   55                   | push                ebp
            //   8bec                 | mov                 ebp, esp
            //   81ece0060000         | sub                 esp, 0x6e0
            //   53                   | push                ebx

        $sequence_3 = { ff15???????? 8d857cffffff 50 e8???????? 85c0 59 7429 }
            // n = 7, score = 100
            //   ff15????????         |                     
            //   8d857cffffff         | lea                 eax, [ebp - 0x84]
            //   50                   | push                eax
            //   e8????????           |                     
            //   85c0                 | test                eax, eax
            //   59                   | pop                 ecx
            //   7429                 | je                  0x2b

        $sequence_4 = { eb34 8d859cfeffff 50 ff15???????? 8d859cfeffff 68???????? 50 }
            // n = 7, score = 100
            //   eb34                 | jmp                 0x36
            //   8d859cfeffff         | lea                 eax, [ebp - 0x164]
            //   50                   | push                eax
            //   ff15????????         |                     
            //   8d859cfeffff         | lea                 eax, [ebp - 0x164]
            //   68????????           |                     
            //   50                   | push                eax

        $sequence_5 = { 56 ff15???????? 68???????? 56 ff15???????? 8d85a4feffff }
            // n = 6, score = 100
            //   56                   | push                esi
            //   ff15????????         |                     
            //   68????????           |                     
            //   56                   | push                esi
            //   ff15????????         |                     
            //   8d85a4feffff         | lea                 eax, [ebp - 0x15c]

        $sequence_6 = { eb19 833801 7407 b800000800 eb0d 8b4004 }
            // n = 6, score = 100
            //   eb19                 | jmp                 0x1b
            //   833801               | cmp                 dword ptr [eax], 1
            //   7407                 | je                  9
            //   b800000800           | mov                 eax, 0x80000
            //   eb0d                 | jmp                 0xf
            //   8b4004               | mov                 eax, dword ptr [eax + 4]

        $sequence_7 = { 8d8568feffff 6804010000 50 56 ff15???????? 8d8568feffff 50 }
            // n = 7, score = 100
            //   8d8568feffff         | lea                 eax, [ebp - 0x198]
            //   6804010000           | push                0x104
            //   50                   | push                eax
            //   56                   | push                esi
            //   ff15????????         |                     
            //   8d8568feffff         | lea                 eax, [ebp - 0x198]
            //   50                   | push                eax

        $sequence_8 = { 56 8b4304 8945f8 8b03 0fb74814 6683780600 8d740118 }
            // n = 7, score = 100
            //   56                   | push                esi
            //   8b4304               | mov                 eax, dword ptr [ebx + 4]
            //   8945f8               | mov                 dword ptr [ebp - 8], eax
            //   8b03                 | mov                 eax, dword ptr [ebx]
            //   0fb74814             | movzx               ecx, word ptr [eax + 0x14]
            //   6683780600           | cmp                 word ptr [eax + 6], 0
            //   8d740118             | lea                 esi, [ecx + eax + 0x18]

        $sequence_9 = { c645ee68 c645ef70 885df0 ff15???????? 8bf8 3bfb 897df8 }
            // n = 7, score = 100
            //   c645ee68             | mov                 byte ptr [ebp - 0x12], 0x68
            //   c645ef70             | mov                 byte ptr [ebp - 0x11], 0x70
            //   885df0               | mov                 byte ptr [ebp - 0x10], bl
            //   ff15????????         |                     
            //   8bf8                 | mov                 edi, eax
            //   3bfb                 | cmp                 edi, ebx
            //   897df8               | mov                 dword ptr [ebp - 8], edi

    condition:
        7 of them and filesize < 344064
}

[TLP:WHITE] win_fatal_rat_w0 (20210820 | Detects FatalRAT, unpacked malware.)

rule win_fatal_rat_w0 {
    meta: 
        author = "AT&T Alien Labs" 
        description = "Detects FatalRAT, unpacked malware." 
        type = "malware" 
        sha256 = "ec0dcfe2d8380a4bafadb3ed73b546cbf73ef78f893e32202042a5818b67ce56" 
        reference = "https://cybersecurity.att.com/blogs/labs-research/new-sophisticated-rat-in-town-fatalrat-analysis"
        copyright = "Alienvault Inc. 2021" 
        malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.fatal_rat"
        malpedia_rule_date = "20210820"
        malpedia_version = "20210820"
        malpedia_license = "CC BY-NC-SA 4.0"
        malpedia_sharing = "TLP:WHITE"
    strings: 
        $decrypt_func = {EC 0F B6 45 10 99 B9 AB 05 00 00 56 F7 F9 8B 75 0C 80 C2 3D 85 F6 76 0F 8B 45 08 8A 08 32 CA 02 CA 88 08 40 4E 75 F4 5E 5D C3} 
        $s1 = "SVP7-Thread running..." 
        $s2 = "nw_elf.dll" 
    condition: 
        uint16(0) == 0x5a4d and all of them
}

Download all Yara Rules

FatalRat Propose Change

References

Yara Rules

FatalRat