SYMBOLCOMMON_NAMEaka. SYNONYMS
win.lambload (Back to overview)

LambLoad

aka: OfficeCertTea

Actor(s): Lazarus Group

VTCollection    

According to Microsoft, this is a downloader used in a supply chain attack involving a malicious variant of an application developed by CyberLink. It is centered around a legitimate CyberLink application installer that has been modified to include malicious code that downloads, decrypts, and loads a second-stage payload. The file, which was signed using a valid certificate issued to CyberLink Corp., is hosted on legitimate update infrastructure owned by CyberLink and includes checks to limit the time window for execution and evade detection by security products.

References
2023-11-22 ⋅ Microsoft ⋅ Microsoft Threat Intelligence
Diamond Sleet supply chain compromise distributes a modified CyberLink installer
LambLoad
2023-10-04 ⋅ Virus Bulletin ⋅ Peter Kálnai
Lazarus Campaigns and Backdoors in 2022-23
SimpleTea POOLRAT 3CX Backdoor BLINDINGCAN CLOUDBURST DRATzarus ForestTiger ImprudentCook LambLoad LightlessCan miniBlindingCan PostNapTea SecondHandTea SnatchCrypto wAgentTea WebbyTea WinInetLoader
2023-04-12 ⋅ Kaspersky Labs ⋅ Seongsu Park
Following the Lazarus group by tracking DeathNote campaign
Bankshot BLINDINGCAN ForestTiger LambLoad LPEClient MimiKatz NedDnLoader Racket Downloader Volgmer
2022-09-30 ⋅ ESET Research ⋅ Peter Kálnai
Amazon‑themed campaigns of Lazarus in the Netherlands and Belgium
BLINDINGCAN FudModule HTTP(S) uploader LambLoad TOUCHMOVE
Yara Rules
[TLP:WHITE] win_lambload_auto (20260917 | Detects win.lambload.)
rule win_lambload_auto {

    meta:
        author = "Felix Bilstein - yara-signator at cocacoding dot com"
        date = "2026-09-17"
        version = "1"
        description = "Detects win.lambload."
        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.lambload"
        malpedia_rule_date = "20260916"
        malpedia_hash = "53a643781c18e08f4a50949af60172d837a0b6f6"
        malpedia_version = "20260917"
        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 = { 33d2 8a93980f0710 8a5f01 47 8954241c 83e37f }
            // n = 6, score = 100
            //   33d2                 | xor                 edx, edx
            //   8a93980f0710         | mov                 dl, byte ptr [ebx + 0x10070f98]
            //   8a5f01               | mov                 bl, byte ptr [edi + 1]
            //   47                   | inc                 edi
            //   8954241c             | mov                 dword ptr [esp + 0x1c], edx
            //   83e37f               | and                 ebx, 0x7f

        $sequence_1 = { ff15???????? 33c0 eb57 8d45f0 50 }
            // n = 5, score = 100
            //   ff15????????         |                     
            //   33c0                 | xor                 eax, eax
            //   eb57                 | jmp                 0x59
            //   8d45f0               | lea                 eax, [ebp - 0x10]
            //   50                   | push                eax

        $sequence_2 = { 7705 3b550c 76c9 8b450c }
            // n = 4, score = 100
            //   7705                 | ja                  7
            //   3b550c               | cmp                 edx, dword ptr [ebp + 0xc]
            //   76c9                 | jbe                 0xffffffcb
            //   8b450c               | mov                 eax, dword ptr [ebp + 0xc]

        $sequence_3 = { 57 ffb6a4b40100 e8???????? 6a00 6a00 8d4dfc 51 }
            // n = 7, score = 100
            //   57                   | push                edi
            //   ffb6a4b40100         | push                dword ptr [esi + 0x1b4a4]
            //   e8????????           |                     
            //   6a00                 | push                0
            //   6a00                 | push                0
            //   8d4dfc               | lea                 ecx, [ebp - 4]
            //   51                   | push                ecx

        $sequence_4 = { 8d4edb 83f953 0f8761040000 33d2 8a9148110210 ff249518110210 48 }
            // n = 7, score = 100
            //   8d4edb               | lea                 ecx, [esi - 0x25]
            //   83f953               | cmp                 ecx, 0x53
            //   0f8761040000         | ja                  0x467
            //   33d2                 | xor                 edx, edx
            //   8a9148110210         | mov                 dl, byte ptr [ecx + 0x10021148]
            //   ff249518110210       | jmp                 dword ptr [edx*4 + 0x10021118]
            //   48                   | dec                 eax

        $sequence_5 = { 8d4802 668b10 83c002 6685d2 75f5 8bb5d0f4ffff }
            // n = 6, score = 100
            //   8d4802               | lea                 ecx, [eax + 2]
            //   668b10               | mov                 dx, word ptr [eax]
            //   83c002               | add                 eax, 2
            //   6685d2               | test                dx, dx
            //   75f5                 | jne                 0xfffffff7
            //   8bb5d0f4ffff         | mov                 esi, dword ptr [ebp - 0xb30]

        $sequence_6 = { 32d1 8895e8330710 45 81fdff030000 7c02 33ed }
            // n = 6, score = 100
            //   32d1                 | xor                 dl, cl
            //   8895e8330710         | mov                 byte ptr [ebp + 0x100733e8], dl
            //   45                   | inc                 ebp
            //   81fdff030000         | cmp                 ebp, 0x3ff
            //   7c02                 | jl                  4
            //   33ed                 | xor                 ebp, ebp

        $sequence_7 = { 03048d00490710 eb02 8bc2 f6402480 7418 e8???????? }
            // n = 6, score = 100
            //   03048d00490710       | add                 eax, dword ptr [ecx*4 + 0x10074900]
            //   eb02                 | jmp                 4
            //   8bc2                 | mov                 eax, edx
            //   f6402480             | test                byte ptr [eax + 0x24], 0x80
            //   7418                 | je                  0x1a
            //   e8????????           |                     

        $sequence_8 = { 6aff 8d85ecfdffff 50 ff7308 66a5 }
            // n = 5, score = 100
            //   6aff                 | push                -1
            //   8d85ecfdffff         | lea                 eax, [ebp - 0x214]
            //   50                   | push                eax
            //   ff7308               | push                dword ptr [ebx + 8]
            //   66a5                 | movsw               word ptr es:[edi], word ptr [esi]

        $sequence_9 = { 4d 3882980f0710 74ec 83fd03 7e1b }
            // n = 5, score = 100
            //   4d                   | dec                 ebp
            //   3882980f0710         | cmp                 byte ptr [edx + 0x10070f98], al
            //   74ec                 | je                  0xffffffee
            //   83fd03               | cmp                 ebp, 3
            //   7e1b                 | jle                 0x1d

    condition:
        7 of them and filesize < 1039360
}
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