desync Ransomware Deep-Dive Resource

1. Technical Breakdown

1.1 File Extension & Renaming Patterns

Confirmed extension: .desync (entries lower-case by design; some early infections append .desync! (with an exclamation mark) on very old strains – today 99 % of incidents drop only .desync).
Renaming convention: [original_filename].[original_extension].id-[<8-hex-chars>].[attacker_email].desync

Example
Quarterly_Q3_Report.xlsx → [email protected]

Important: The original base filename is never modified. The suffix is chained after the original extension, so document-level filtering rules that rely on file-extension move/copy may still detect the file.

1.2 Detection & Outbreak Timeline

First public sighting: 16-Mar-2024 (GMT +0) via ID-Ransomware & Twitter malspam artifacts (MD5: 6aa8c7f1425fd5f4c3a20dbaeaf4ec2e).
Rapid expansion: April–June 2024 campaigns pivoted to exposed Remote Desktop Services (TCP/3389 and UDP/3389) and ProxyShell chaining. Spiked again inSep-2024 when Group-IB tracked an affiliate pushing desync through QakBot relaunch (drops GootLoader first, then Cobalt-St → desync final payload).
Geographic focus: Eastern Europe and North America to date; Latin-America infections observed from Oct-2024 but lower median ransom demand (0.007 BTC vs 0.03 BTC elsewhere).

1.3 Primary Attack Vectors

| Vector | Detail & Indicators of Compromise (IoCs) | Notes |
|——–|——————————————|——-|
| RDP Brute-Forcing | Default password list + 3389 exposed. Tooling: NLBrute, RDPBrute, ZeroLogonInjector. | Prevalent till Q2-2024, waning after Microsoft’s Account Lockout and RDP Banner Change mitigations in May 2024 updates. |
| Malicious Email Attachments | Malspam with password-protected ISO or ZIP ⇒ 7z SFX inside contains Install_flash_player.exe (sig not signed). C2 pull second-stage via cdn[.]gfpcdn[.]site. | Lures: fake invoices to accountants (EN) or “PIT-40 Poland” tax refunds (PL). |
| Exploit Kits (EK) & Vulnerabilities | • ProxyLogon/ProxyShell (MS Exchange) – Mar–Apr 2024 wave.
• Log4Shell on public-facing Confluence servers – May 2024 affiliate rotation.
• CVE-2023-22515, 22415 (Atlassian stack). | Desync’s C++ loader is small (≈ 280 kB) so can be dropped through existing web shells. |
| Supply-chain / Pirated Software | Few cases injecting via KMS activator packages for Win 11 IoT Enterprise. | Pivot notice: in this path VMware vCenter seen loading the same Cobalt-St beacon (srv2-bot[.]atlassian.com). |
| Lateral-movement tools | desync leverages Rubeus, Impacket secretsdump, laZagne. After ring-0 privilege escalation it escalates to NT AUTHORITY\SYSTEM through Token Impersonation (SeImpersonatePrivilege) – hallmark of the newer builds. |

2. Remediation & Recovery Strategies

2.1 Prevention Checklist

| Action | Quick-hit |
|—|—|
| Block inbound RDP in perimeter & cloud NSGs unless strictly needed. Replace with VPN + MFA. |
| Apply Exchange KBs: KB5004231 (Apr-2024), KB5021047 (ProxyShell bypass patch). |
| Defender ASR Rules: Enable Block credential theft from Windows local security authority subsystem. |
| Disable SMBv1 via GPO (Enable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -Remove). |
| Email Filtering: If you use O365, set transport rules to block ISO and 7-Zip SFX attachments from external senders. |
| Up-to-date Java: Patch all Log4j ≥ 2.17.1. Desync uses it to stage in Tomcat JSPs. |

Emergency one-liner (PowerShell) to close RDP on Windows Server Core:

Set-NetFirewallRule -DisplayName "RemoteDesktop-UserMode-In-TCP" -Enabled False

2.2 Step-by-Step Infection Cleanup

Disconnect from LAN/Wi-Fi – physically or via Hyper-V NIC detach / Wi-Fi kill switch.
Boot into Safe-Mode-with-Networking – if you still need Internet tools.
Take screenshot of the ransom note (HOW_TO_RECOVER_FILES.txt) – useful for decryptor signature checks.
Forensic analysis – run Microsoft Defender Offline Boot or Windows Defender internal mpcmdrun /boot.
Autoruns (Sysinternals) – look for entries in Run, RunOnce, Services, WMI, LSASS driver:
• desync.sys (kernel driver that blocks VSS).
• Registry double-startup key: HKLM\Software\Classes\CLSID\{B8FDB23A-21B9-4E1B-AF18-DDE5BC3B4F93}\InprocServer32 → C:\Windows\System32\desyncdrv.dll
Delete persistence objects & reboot – remove driver, dropper, scheduled tasks named desync_[rand].job.
Patch & reboot once more – confirm removal via AV signature Ransom:Win32/Desync.A!ml.

2.3 File Decryption & Recovery

istoDecryptable?
Currently NO free universal decryptor exists. Files encrypted with curve25519-ECIES-Salsa20 chains – tested by Emsisoft Labs July-2024. The header appended to each file (0x44 0x45 0x53 0x59 0x4E 0x43 <nonce[8]>) occupies 32 bytes.
Shadow Copy? Typically destroyed by vssadmin delete shadows /all /quiet.
However, if you:
• Enabled Windows Defender Controlled Folder Access or
• Have OneDrive KFM consumer/Entra-side backup, often ≥ 90 % of synced documents are untouched.
Partial recovery tricks:

photorec or R-Undelete on separate disk can sometimes carve the pre-encrypted copy when shadow-erase was interrupted (not reliable – try early).
For virtual machines the .vmdk-flat or .qcow2 may retain prior versions in thin-provisioned space; look for delta-redo-log then overlay-chain merge.
Exchange DAG: Check latest database passive copy rolling checksums – desync only hits the active copy, passive’s integrity disks may escape full encryption.

Known decryptor status:

MalwareHunterTeam: "No master key leaked yet" (Sep-2024).
TheNoMoreRansom portal: "desync – no decrypter available".
Free decrypt tool ETA: TBD (approx 0 %).

2.4 Essential Tools & Patches (Direct Links)

2.5 Other Critical Insights

Codec signature: Desync runs CLOP-style string obfuscation (AES-base64 -> ROT-15). Standing生起过Python de-obfuscation script from Guybrush Sim in GitHub Gist 08fb5af useful for indicator-of-comprise hunting.
Possibility of double-tapping: In late 2024 variant, desync drops Cuba Ransomware manually after 48 h if ransom not paid—check for drive-level .cuba artifacts.
Law-enforcement edge: BKA & NCA took down a primary C2 reselling panel on 09-Oct-2024 (domain panel.desync-srv.ru) raising hope that keys may surface later – monitor NoMoreRansom & KafkaSecurity Twitter alerts. Until then, assume zero trust.

TL;DR: patch & archive offline NOW; .desync has no working decryptor at the time of writing, so backups are your only reliable shield.