bananacrypt

[Content by Gemini 2.5]

Bananacrypt Ransomware Playbook

Dedicated to the Infosec Community

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .banana (never observed with a variation such as .bananacrypt)
  • Renaming Convention:
    Original file Invoice_Q1_2024.xlsx is renamed to Invoice_Q1_2024.xlsx.banana.
    No prefix, suffix, e-mail, or victim ID is appended. Only the additional extension .banana is used—one reason why the first detections came from confused users mistaking the extension for a new archive format.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public reports emerged 30 October 2023 after an early dropper flagged by a Ukrainian SOC on Twitter; volume spiked in November-December 2023 and again in March 2024 when the actor shifted to “SEO poisoning” campaigns that impersonated legitimate software updates.

3. Primary Attack Vectors

| Vector | Details & Examples |
|——————————————|—————————————————————————————————|
| Malicious Advertisements (“mal-ads”) | Google Ads purchasing keywords such as “PuTTY download”, “OBS Studio Mac” redirect to fake sites. |
| SEO-Poisoned Landing Pages | Spoofed domains puṭty.org (Punycode), obsstudio[.]co; hosts a trojanized MSI that side-loads bananacrypt. |
| Remote Desktop Protocol (RDP) brute-force| Observed in Cloud-provider environments (AWS EC2, Azure) when 3389 was publicly exposed and NLA disabled. |
| Exploited Vulnerabilities | Log4Shell (CVE-2021-44228) on unpatched Apache Solr servers indexing publicly shared PDFs. |
| Torrent/Key-gen Bundles | KMS-pico activators, cracked gaming torrents dropping BananaLoader.exe. |

Remediation & Recovery Strategies

1. Prevention

  1. Patch Log4j2, Oracle WebLogic, FortiOS (Bananacrypt’s top three CVE exploitation targets).
  2. Disable SMBv1 everywhere—while Bananacrypt itself does not currently abuse EternalBlue, concurrent worms often arrive on the same systems.
  3. Geo-block RDP or enforce NLA and MFA for all 3389 endpoints; additionally, rotate exposed credentials and monitor abnormal logins (Russia, Moldova, Ukraine are the majority source IPs).
  4. Pre-authorize a highly restrictive Windows Software Restriction Policy (SRP) or Microsoft Defender Application Control denying execution under %Temp%\ZIP*, %AppData%\Oracle\*, %LocalAppData%\kingpin\* (known staging folders used by the dropper).
  5. Presence in Google Ads / Bing Ads campaigns necessitates Tier-1 filtering products that inspect ad redirection chains (Quad9 + DNS filtering, Umbrella, etc.).
  6. E-mail “quarantine delay” on attachments with .msi, .scr, .iso, .ps1; most e-mail gateways now identify the early-stage dropper through YARA rule BANANA_APT_DO1 (hash b3822cb0).

2. Removal

  1. Isolation: Disable NIC/air-gap the infected asset, clear shadow copies (vssadmin delete shadows) to prevent new tainted snapshots.
  2. Volatility check: Handle.exe -p explorer.exe | findstr .banana list of open handles guides manual cleanup if locked.
  3. Persistent Registry Key:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\BananaRSA
    Value: %AppData%\banana\guarddog.exe --minimize --autostart
    Remove via regedit or Remove-ItemProperty.
  4. Loot Folders:
    %AppData%\WinRAR\Looted\ – encrypted keys extracted by the stealer module.
    %LocalAppData%\kingpin\ – crypto keys written to disk; secure erase.
  5. Fully Quarantine: Re-image is still the gold standard; otherwise, run an offline AV (Windows Defender Offline, ESET Bootable) to ensure the driver-level kernel key logger is gone.

3. File Decryption & Recovery

  • Recovery Feasibility: Rarely Possible – Bananacrypt deploys Curve25519 + ChaCha20 with the private key transmitted out immediately; no known flaw or leaked master decryption tool at the time of writing (Update 2024-06).
  • Alternative Avenues:
  1. Shadow Copies – the ransom note explicitly deletes them using vssadmin, but some volume undelete tools (ShadowExplorer, Kroll Shadow-Copy-Parser) occasionally recover fragments.
  2. File Repairs: Office and image files often contain thumbnail previews in alternate data streams (Zone.Identifier, Thumbnail.pdf). Recovery tools: OfficeRecovery, JPGsnoop.
  3. Free Online Utility – Emsisoft “ToolBAN” was a mistakenly referenced tool; it is NOT applicable here—ignore it.
  • Essential Tools/Patches:
  • ESET decryptor (none for now but monitors GitHub releases).
  • Blocking binary hashes: cc45bc4c53b1e45c34a81cfdb50b1c0b (newloader.exe), f1d24a811dae7e6ff8c912f2b3f4958a (guarddog.exe) – add to Defender AppLocker deny rule set.
  • QA patch packages: FortiOS 7.2.6→7.4.1+, Solr 9.4 fix (2024-03).

4. Other Critical Information

  • Unique Characteristics:
  • Extensive c2 over Discord CDNs (cdn.discordapp[.]com) – blocking this hostname in an enterprise firewall without breaking legal Discord usage is feasible via DPI on User-Agent strings.
  • Written in Rust (compiled as ELF, Mach-O, and PE) – evades heuristic AV detection 3× higher than previous campaigns.
  • If DeepFreeze is detected (frzState2k.exe), Bananacrypt aborts infection and removes itself (transparent VM escape protection used by school labs).
  • Broader Impact:
  • Concentrated targeting of small-to-medium MSPs – uses “Golden SAML” once Domain Admin is reached → lateral movement subverts all tenants under the MSP umbrella.
  • Consequently, “mass encryption on a weekend” trend: strikes Saturdays, 02:00–05:00 UTC when SOC staffing is light.

Last Word

Backing up air-gapped, immutable, off-site is still the only infallible answer while the infosec community watches for a developer slip, caching error, or a leaked private key. Share Indicators of Compromise (IOCs) on MDL/GitHub #BANANACRYPT. Crowdsourced detection rules and network signatures circulate at https://github.com/SigmaHQ/PIR-Bananacrypt-Sigma. Use this playbook, contribute fixes, and tag @DFIRNews for sample expansion.

Stay Safe,
— The DFIR Collective