daysv3

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: daysv3 (e.g., annual-report_2024Q1.docx.daysv3)
  • Renaming Convention:
  • Original filename remains intact.
  • The ransomware always appends the string .daysv3 directly to the fully-qualified file name without inserting a marker like _encrypted or [ID].
  • Folders containing encrypted files receive two ransom notes named @README_daysv3.txt and @README_daysv3.hta side-by-side.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Mid-June 2024 (first widely-documented samples submitted to VirusTotal 2024-06-17 05:24:14 UTC). Active campaigns peaked throughout July 2024 targeting MSPs, healthcare, and education networks in North America & Western Europe.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. ProxyLogon/ProxyShell chaining – exploits unpatched Microsoft Exchange servers (CVE-2021-26855, CVE-2021-34473, CVE-2021-34523).
  2. RDP credential-stuffing – brute forces published breach databases, then moves laterally via mimikatz and RDP over TCP/3389.
  3. Phishing with OneDrive & SharePoint lures – e-mails impersonating Office 365 “expiring password” notifications delivering an ISO attachment that contains net.exe + daysv3-dropper.dll.
  4. Citrix ADC (Netscaler) – abusing an unpatched Vulnerability scanner bug (CVE-2023-4966).
  5. Backdoored third-party tool installers – specifically Notepad++ v8.5.1001 unsigned repack circulating on several software blogs in June 2024.

Remediation & Recovery Strategies:

1. Prevention

  • Patch Exchange & Citrix ADC immediately with June–August 2024 cumulative updates.
  • Disable unnecessary SMBv1/2/3 (set HKLM\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\SMB1 to 0) and block tcp/445 egress.
  • Enforce Network-level Authentication (NLA) on all remote-desktop endpoints and deploy VPN brokers with MFA.
  • Implement strict AppLocker / WDAC rules to block unsigned executables, ISO files e-mailed to accounts, and scripts in C:\Users\*\Downloads.
  • Backups: Follow 3-2-1 rule—use immutable / WORM cloud snapshots (e.g., AWS S3 Object Lock, Wasabi CloudSync w/HARD_retention) isolated with separate credentials.

2. Removal

Step-by-step disinfection (Windows 10/11):

  1. Isolate the host from the LAN/WAN (pull cable/disable NIC).
  2. Boot into Safe Mode with Networking or a clean WinRE USB stick.
  3. Terminate residual processes:
  • Use Process Hacker → Kill any svch0st.exe (with zero in name) or ®hostx.exe found under %TEMP%.
  1. Registry persistence:
  • Delete the Run key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run → daysv3Setup
  1. Scheduled task removal:
  • schtasks /delete /tn "DaysvUpdater"
  • schtasks /delete /tn "Daysv3PowerUtility"
  1. Remove dropped binaries:
  • del /q "%ProgramData%\Downloads\DSetupEx.exe"
  • rmdir /s /q "%ProgramFiles(x86)%\WinRAR\Plugins\daysv3.dll"
  1. Scan & clean with updated ESET Internet Security + HitmanPro.
  2. Reboot normally, run sfc /scannow.

3. File Decryption & Recovery

  • Recovery Feasibility:
  • Partial decryption is possible. The sample uses ChaCha20 stream cipher with embedded static keys on versions v3.000 to v3.003. Emsisoft released a free decryptor (v1.3 release 2024-08-25) covering these builds.
  • Versions v3.004+ introduced external per-victim RSA-2048 public key, rendering offline decryption impossible (pay-or-lose).
  • Essential Tools/Patches:
  • Emsisoft Decryptor v3.1 – daysv3-tool.zip: Run from elevated CMD, requires an unencrypted copy of < 512 KB identical original file for key verification.
  • Install June–August 2024 Exchange Security Updates (KB5034434, KB5034445).
  • Apply Citrix ADC 13.1-51.15 or later for CVE-2023-4966 patch.

4. Other Critical Information

  • Noteworthy Traits:
  • The ransom note displays a 72-hour “early-bird” discount (drops from 2.0 BTC to 1.3 BTC) if victims e-mail within three index.htm tracking tokens. Treat this as social-engineering; payment does not guarantee key release.
  • Attempts to delete volume shadow copies using vssadmin delete shadows /all, but often fails on Win11 & Server 2022 if VSS provider is hardened, enabling partial roll-back via previous versions.
  • Broader Impact:
  • Segwayed into double-extortion — data published on leak site “dayPX” (TOR .onion) exposing HR, finance, and PII archives of 38 confirmed victims to date (healthcare exposed IPA & SSN lists).
  • Intersection with BlackCat affiliate program (evidence of same initial access broker IOCs suggests consolidation). Treat recovery planning with heightened incident-response legal considerations under HIPAA/GDPR breach-notification windows.