Krybit Ransomware — RaaS Double-Extortion Attack Chain

Krybit is a Ransomware-as-a-Service operation first observed in the wild in late March 2026 (independent underground monitoring recorded its first detection on April 3, 2026). It runs a standard affiliate model — an 80/20 revenue split in affiliates' favor — with builders for Windows, Linux, VMware ESXi, and NAS devices, and pressures victims through double extortion: data is staged and exfiltrated (10GB–250GB observed per victim) before files are encrypted, and payment is pursued through a Tor-based data leak site plus direct Tox-messenger negotiation. Captured samples are flagged by multiple antivirus engines as derivatives of the leaked 2021 Babuk source code (ESET: Filecoder.Babyk.A; Microsoft: Babuk!ic; Combo Cleaner: Ransom.Babuk) rather than a custom-engineered encryptor.

In April 2026, Krybit became unusually well-documented for a group its age: a rival RaaS operator, 0APT, breached Krybit's affiliate panel and published its contents (2 administrators, 5 affiliates, 20 victims in active negotiation, ransom demands of $40,000–$100,000, five reused Bitcoin wallets with zero recorded transactions, and plaintext-stored credentials). Krybit retaliated within 48 hours, compromising 0APT's own server and proving that 190+ of 0APT's claimed victims were entirely fabricated. That mutual breach is the source of most of the atomic indicators in this pack (Tox IDs, .onion domains, wallet addresses) — it is a striking story, but it is secondary to this pack's purpose. SOCRadar's live tracker shows Krybit has continued operating undisturbed since: 157 total claimed attacks and 141 catalogued victims across 57 countries as of the September 8, 2026 tracker update, spanning Professional Services (21.4%), Technology (17.1%), and Manufacturing (14.3%) as the top targeted sectors.

The highest-value defensive angle is the group's one consistently documented pre-encryption behavior: prior to encrypting, Krybit executes vssadmin.exe delete shadows /all /quiet to destroy Volume Shadow Copies and disable built-in Windows recovery. That single command is the best-corroborated, lowest-false-positive detection opportunity this pack has (Section 8, Q1). The second-highest-value angle is initial-access hardening: SOCRadar's ATT&CK tagging shows only two confirmed techniques for how Krybit affiliates get in — Valid Accounts (T1078) and RDP (T1021.001) — which means MFA on remote-access surfaces and RDP exposure reduction address the group's entire confirmed initial-access surface. Everything else in Krybit's chain (execution, persistence, defense evasion, discovery) is described only narratively in public reporting, with no specific tool, LOLBin, or injection technique named — this pack is explicit about that gap rather than inventing detail to fill it (see Sections 6 and 15).

Defender priority: treat any confirmed execution of vssadmin.exe delete shadows, wmic shadowcopy delete, or bcdedit /set {default} recoveryenabled no on a production host as an active or imminent ransomware event, not a false alarm to triage later — isolate the host immediately per Section 14. In parallel, enforce MFA on every RDP/VPN/remote-administration interface and eliminate direct internet exposure of RDP; these two controls cover Krybit's only publicly confirmed initial-access techniques. Maintain immutable or offline backups that a compromised RDP/valid-account session cannot reach or delete — shadow-copy destruction is worthless to the attacker against a backup it cannot touch.

Six sources were fetched and saved in full to Krybit-Ransomware-Hunt-sources/ for this pack. Two (both socradar.io) initially returned HTTP 403 to direct/automated fetches and were retrieved instead through a text-extraction proxy; their content was cross-checked for internal consistency (dates, figures, IOC values) before use and shows no sign of tampering. No fetched source contained any text addressed to an AI agent, instructions to execute commands, or attempts to redirect this research process — all six are ordinary article/report/tracker content and are cited below. One material discrepancy was found and is called out explicitly rather than silently resolved: WatchGuard's tracker entry names the ransom note README-RECOVER.txt (reversed word order), while SOCRadar (two independent mentions) and Picus both give RECOVER-README.txt. This pack ships RECOVER-README.txt as the primary indicator (majority-sourced and matching the operational-intel candidate list) and carries the WatchGuard variant as a secondary pattern in both the IOC table and the CQL detection (Section 8, Q8) rather than dropping it.

Decision: the 0APT-vs-Krybit feud (server compromise mechanics, 0APT's fabricated victims, the Android-phone infrastructure) is summarized only as context in Sections 1 and 3 — it explains where several atomic IOCs in this pack come from, but it is not itself a detection surface for a Falcon-monitored enterprise. All defensive content is built around Krybit's own confirmed TTPs against a typical victim, not the inter-gang conflict.

Hypothesis: A Krybit RaaS affiliate has obtained valid credentials or direct RDP access to the environment (its only two publicly confirmed initial-access techniques), is staging or has already staged data for exfiltration, and is preparing to or has already executed vssadmin-based shadow-copy destruction ahead of deploying a Babuk-derived encryptor that appends .KRYBIT to affected files and drops a RECOVER-README.txt ransom note directing the victim to a Tor negotiation panel.

The four MD5 hashes above come from SOCRadar's live IOC feed with no accompanying malware-family label, file size, or first-seen date in the fetched snapshot. Treat them as hunt candidates (search for the hash, do not auto-block on it) until corroborated by a second source or your own sample analysis.

T1567 (Exfiltration Over Web Service) is a plausible technique for the leak-site publication step but is not independently confirmed as a distinct technical vector in any source cited here — T1041 (Exfiltration Over C2 Channel) is the only exfiltration technique SOCRadar formally tags, and this pack does not go beyond that.

These checks supplement Section 8's CQL where Falcon telemetry alone is thin (RDP-specific detail, Tor/Tox network context) or unavailable (organizations without the Identity Protection module).

Windows Security Event Log — RDP logon activity

Where the Falcon Identity Protection module is not licensed, hunt directly in the Windows Security event log on RDP-exposed hosts: Event ID 4624 with LogonType 10 (RemoteInteractive) for successful RDP logons, and Event ID 4625 with LogonType 10 for failures. A burst of 4625/LogonType 10 followed by a 4624 from the same source is the same credential-stuffing-then-success pattern Q3/Q4 hunt for in Falcon telemetry. Also review Event ID 1149 (Terminal Services — RDP network connection successful) on the RDP listener itself.

Volume Shadow Copy Service (VSS) event log

The Windows Application log records VSS provider/writer errors that can follow a vssadmin delete shadows call, and System log Event ID 7036 records the Volume Shadow Copy service changing state. Neither is as reliable as the direct command-line detection in Q1, but both are useful corroboration on hosts where process-command-line logging was disabled or tampered with.

Backup software logs

Review Windows Server Backup, Veeam, or equivalent backup-software logs for VSS snapshot failures or missing backup jobs immediately following a suspected vssadmin execution — a sudden gap in successful backup jobs across multiple hosts in a short window is consistent with active shadow-copy destruction at scale.

Firewall / proxy egress logs — Tor and Tox

Because Tor clients typically resolve .onion addresses through the Tor circuit itself rather than conventional DNS (see the Q9 caveat in Section 8), egress-log review is often more productive than DNS-based detection: look for connections to known Tor entry-node ranges, or for a proxy/firewall CONNECT log entry that literally contains one of the five Krybit .onion strings (Section 10) — this can happen when a negotiation link is pasted into a non-Tor browser or a misconfigured DoH resolver. For Tox, no Krybit-specific client binary or hash has been publicly documented; organizations wanting general Tox-usage visibility can monitor for execution of common Tox client binaries (e.g. qTox, uTox) or outbound traffic on Tox's documented default port UDP/TCP 33445 as a generic protocol-tunneling signal (T1572) — this is public protocol context, not a Krybit-attributed indicator, and is not shipped as an IOC in Section 10 for that reason.

These nine queries target Windows endpoint and identity telemetry — the surface with mature Falcon sensor coverage. Krybit also ships Linux, VMware ESXi, and NAS builders (Section 5); this pack does not include Linux-sensor or ESXi-specific CQL, since no distinct technical detail for those payloads has been published in the sources cited here.

// HUNT: vssadmin Volume Shadow Copy deletion (Krybit pre-encryption step)
// MITRE: T1490
// CONF: high  FP: low  COST: low
// REQUIRES: ProcessRollup2, SyntheticProcessRollup2
// FALSE POSITIVES: none expected -- legitimate shadow-copy deletion via vssadmin is rare outside DR testing
#event_simpleName=/ProcessRollup2|SyntheticProcessRollup2/
| FileName=/^vssadmin(\.exe)?$/i
| CommandLine=/delete\s+shadows/i
| table([ComputerName, UserName, ParentBaseFileName, FileName, CommandLine, @timestamp])

// HUNT: Broader recovery-inhibition command cluster (wmic/bcdedit/wbadmin)
// MITRE: T1490
// CONF: high  FP: medium  COST: low
// REQUIRES: ProcessRollup2, SyntheticProcessRollup2
// FALSE POSITIVES: legitimate DR-testing or backup-maintenance scripts can invoke these same commands
// TUNING: exclude signed DR-testing/backup-admin scripts and their documented service accounts; correlate with Q1 or Q6 before treating as active ransomware
#event_simpleName=/ProcessRollup2|SyntheticProcessRollup2/
| FileName=/^(wmic|bcdedit|wbadmin)(\.exe)?$/i
| CommandLine=/(shadowcopy\s+delete|recoveryenabled\s+no|delete\s+catalog|delete\s+systemstatebackup)/i
| table([ComputerName, UserName, ParentBaseFileName, FileName, CommandLine, @timestamp])

// HUNT: Authentication-failure burst (Valid Accounts abuse precursor)
// MITRE: T1078
// CONF: medium  FP: medium  COST: low
// REQUIRES: ActiveDirectoryAuthenticationFailure (Falcon Identity Protection)
// FALSE POSITIVES: shared VPN/RDS gateway accounts, legitimate password-typo bursts, and account-lockout storms
// TUNING: exclude known VPN/RDS gateway service accounts; tune the 10-failures/5-min threshold to your environment's lockout policy
#event_simpleName=ActiveDirectoryAuthenticationFailure
| Bucket5m := @timestamp - (@timestamp % 300000)
| groupBy([Bucket5m, SamAccountName], function=count(as=Failures), limit=1000)
| Failures>10
| sort(Failures, order=desc, limit=200)
| table([Bucket5m, SamAccountName, Failures])

// HUNT: RDP (RemoteInteractive) logon volume by account/host
// MITRE: T1078, T1021.001
// CONF: low  FP: high  COST: low
// REQUIRES: UserLogon
// FALSE POSITIVES: legitimate IT administration, RDS/Terminal Server farms, and approved remote-support sessions dominate this dataset
// TUNING: exclude known RDS/Terminal Server farms, IT admin jump hosts, and approved remote-support accounts; correlate with Q3 (auth-failure burst) or Q9 (external attacker-infra contact) before treating any row as suspicious
#event_simpleName=UserLogon
| LogonType=10
| groupBy([UserName, ComputerName], function=count(as=RdpLogons), limit=1000)
| sort(RdpLogons, order=desc, limit=200)
| table([ComputerName, UserName, RdpLogons])

// HUNT: Abuse of legitimate system processes (generic defense-evasion net)
// MITRE: T1562, T1055, T1027
// CONF: low  FP: high  COST: low
// REQUIRES: ProcessRollup2, SyntheticProcessRollup2
// FALSE POSITIVES: these LOLBins have extensive legitimate administrative and software-installer use
// TUNING: exclude signed installer/deployment tooling (SCCM, Intune, approved software packagers); no Krybit-specific tool or hash has been publicly named -- treat hits as pivots for further investigation, not standalone alerts
#event_simpleName=/ProcessRollup2|SyntheticProcessRollup2/
| FileName=/^(rundll32|regsvr32|mshta|installutil|regasm|regsvcs)\.exe$/i
| table([ComputerName, UserName, ParentBaseFileName, FileName, CommandLine, @timestamp])

// HUNT: Mass file-touch burst (ransomware encryption behavior)
// MITRE: T1486
// CONF: high  FP: medium  COST: medium
// REQUIRES: RansomwareOpenFile
// FALSE POSITIVES: backup jobs, AV full scans, and large file-copy or migration tasks
// TUNING: exclude known backup/AV-scan/migration service accounts and their scheduled windows; tune the 100-file threshold to your environment's baseline
#event_simpleName=RansomwareOpenFile
| groupBy([ComputerName, UserName], function=count(as=FilesTouched), limit=500)
| FilesTouched > 100
| sort(FilesTouched, order=desc, limit=100)
| table([ComputerName, UserName, FilesTouched])

// HUNT: .KRYBIT ransom-extension file write
// MITRE: T1486
// CONF: high  FP: low  COST: low
// REQUIRES: RansomwareOpenFile -- validate TargetFileName population in your tenant
// FALSE POSITIVES: none expected -- the .KRYBIT extension is campaign-unique, not generic admin tooling
#event_simpleName=RansomwareOpenFile
| TargetFileName=/\.KRYBIT$/i
| table([ComputerName, UserName, TargetFileName, @timestamp])

// HUNT: Krybit ransom-note filename write
// MITRE: T1486
// CONF: high  FP: low  COST: low
// REQUIRES: RansomwareOpenFile -- validate TargetFileName population for non-PE text-file writes in your tenant
// FALSE POSITIVES: none expected -- these exact filenames are campaign-specific, not generic admin tooling
#event_simpleName=RansomwareOpenFile
| TargetFileName=/^(RECOVER-README|README-RECOVER)\.txt$/i
| table([ComputerName, UserName, TargetFileName, @timestamp])

// HUNT: DNS resolution of known Krybit .onion infrastructure
// MITRE: T1071, T1105
// CONF: medium  FP: low  COST: low
// REQUIRES: DnsRequest
// FALSE POSITIVES: none expected -- these five .onion strings are campaign-specific; expect near-zero volume since Tor typically bypasses conventional DNS
#event_simpleName=DnsRequest
| DomainName=/^(krybieodq754vlwufrsuxaswxb5zpxyibaawmed2jaduoz2e5m56hmid|krybitqsdzwmhnitvwuhvsntfgf2wrhxveyxroxpc44c6gkft2cqldyd|krybitx3fh5krdnhegyp2ob3lhizsaiadturtio3ginf7it5gsdgu2yd|krybitxdpxohsmjooeb3gbgpmdddreh6mnflzac6bnezz74b7yje67yd|krybivdln3oc3twbin4budgznzq7dmcolldnsx455lspxxe23b56y5qd)\.onion$/i
| table([ComputerName, UserName, DomainName, ContextProcessId, @timestamp])

Queries not listed above (Q3, Q4, Q5, Q6, Q9) remain investigate-only hunt queries — their FP profile (shared authentication infrastructure, ubiquitous RDP/LOLBin legitimate use, near-zero-baseline Tor DNS) makes them appropriate for scheduled hunting and analyst triage, but not for automated Prevent-mode blocking without heavy environment-specific tuning first.

Playbook 1 — Alert and Prevent on Shadow-Copy Deletion

PLAYBOOK 1 -- Alert and Prevent on shadow-copy deletion (Falcon Custom IOA)

Step 1. Deploy Q1 (Section 8) as a scheduled hunt query and confirm 7+ days of clean baseline.
  Prerequisites: Falcon console access; ProcessRollup2/SyntheticProcessRollup2 flowing fleet-wide.
  Command:  Falcon console -> NG-SIEM / Advanced Event Search -> paste Q1 -> Save as Scheduled Search
    (daily, no time restriction beyond the search window)
  Reboot required: No
  Rollback: Delete or disable the scheduled search if it proves too noisy before tuning is complete.

Step 2. Promote the validated pattern to a Custom IOA in Detect mode.
  Prerequisites: Step 1 complete with zero unexplained benign hits; Falcon Custom IOA rule authoring rights.
  Command:  Falcon console -> Endpoint Security -> Custom IOA Rule Groups -> New Rule Group (Windows) ->
    New Rule -> Process Creation -> ImageFilename matches vssadmin.exe AND CommandLine contains
    "delete shadows" -> Severity: Critical -> Action: Detect
  Reboot required: No (policy pushes on next sensor check-in)
  Rollback: Set the rule's Action back to Monitor/Disabled if it fires on a confirmed-legitimate DR test;
    add the specific service account to an exclusion rather than disabling the rule group entirely.

Step 3. Escalate to Prevent mode.
  Prerequisites: Step 2 running clean in Detect mode for the validation window in Section 11.
  Command:  Same Custom IOA rule -> Action: Prevent
  Reboot required: No
  Rollback: Revert Action to Detect immediately if a legitimate business process is blocked; document
    the exception and add a scoped exclusion before re-enabling Prevent.

Playbook 2 — RDP Exposure Reduction and MFA Enforcement

PLAYBOOK 2 -- RDP exposure reduction and MFA enforcement

Step 1. Inventory all RDP-listening hosts reachable from the internet.
  Prerequisites: Network scanning tool or firewall rule-set export; asset inventory.
  Command:  External scan for TCP/3389 exposure, cross-referenced against the firewall rule base
  Reboot required: No
  Rollback: N/A (assessment step)

Step 2. Remove direct internet exposure; route all RDP through a VPN or jump host.
  Prerequisites: Existing VPN/jump-host infrastructure, or budget to stand one up.
  Command:  Firewall rule change closing inbound TCP/3389 from "any", replaced with a rule scoped to
    the VPN/jump-host subnet only
  Reboot required: No
  Rollback: Re-open the prior rule temporarily only for a documented, time-boxed exception, tracked to
    closure.

Step 3. Enforce MFA on the VPN/jump-host authentication path and on Network Level Authentication (NLA)
  for RDP itself.
  Prerequisites: MFA provider integrated with the VPN/jump-host and, where supported, RDS Gateway.
  Command (PowerShell, enable NLA):
    Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" `
      -Name "UserAuthentication" -Value 1 -Type DWord -Force
  Reboot required: Yes -- RDP service restart required for the NLA change to take effect.
  Rollback:
    Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp" `
      -Name "UserAuthentication" -Value 0 -Type DWord -Force
    then restart the RDP service. Roll back only if a legacy client that cannot negotiate NLA must
    connect, and track remediation of that client to closure.

Step 4. Verify with a benign test.
  Prerequisites: A non-production test host with RDP enabled.
  Command:  Attempt an RDP connection from a client that does not support NLA and confirm it is rejected;
    confirm a supporting client is prompted for credentials before the full session establishes.
  Reboot required: No
  Rollback: N/A (verification step)

Playbook 3 — Immutable/Offline Backup Verification

PLAYBOOK 3 -- Immutable/offline backup verification

Step 1. Identify every host holding data in scope for Krybit's target sectors/systems, and confirm which
  currently rely solely on Volume Shadow Copies (i.e., no offsite/immutable copy).
  Prerequisites: Backup software inventory and configuration export.
  Command:  Review backup job configuration for "immutable", "air-gapped", or "offline" retention
    settings on each job; flag any job whose only retention is local VSS snapshots
  Reboot required: No
  Rollback: N/A (assessment step)

Step 2. For any host relying solely on VSS, configure an immutable or offline backup copy.
  Prerequisites: Backup infrastructure supporting immutability (S3 Object Lock equivalent, tape,
    air-gapped replica, or a backup vendor's native immutability feature).
  Command:  Vendor-specific -- e.g., enable immutable/WORM retention on the backup repository and set a
    minimum retention lock period covering your expected detection-to-recovery window
  Reboot required: No
  Rollback: Reduce the retention lock period only via the vendor's documented emergency-override process,
    which should itself require secondary approval -- a lock an attacker (or a rushed admin) can casually
    remove is not actually immutable.

Step 3. Test restoration from the immutable/offline copy.
  Prerequisites: An isolated recovery environment, not production.
  Command:  Perform a full restore of a representative dataset to the isolated environment and validate
    data integrity
  Reboot required: No (restore target is isolated)
  Rollback: N/A (test step; document results and any gaps found)

Step 4. Schedule recurring restoration tests (at minimum quarterly) and track pass/fail per host group.
  Prerequisites: Step 3 complete at least once.
  Command:  Add the restoration test to the standing DR test calendar
  Reboot required: No
  Rollback: N/A

Playbook 4 — EDR Tamper Protection and Broad Process Logging

PLAYBOOK 4 -- EDR tamper protection and broad process logging (T1562/T1055/T1027 coverage gap)

Step 1. Enable Falcon Sensor Tampering Protection (if not already enabled).
  Prerequisites: Falcon console admin access; sensor policy edit rights.
  Command:  Falcon console -> Host Setup and Management -> Sensor Update Policies -> [policy] ->
    enable "Sensor Tampering Protection"
  Reboot required: No
  Rollback: Disable the same toggle in the sensor policy if it conflicts with an approved
    endpoint-management tool; document the exception.

Step 2. Confirm process-command-line and script-block logging is enabled fleet-wide.
  Prerequisites: Group Policy or equivalent endpoint-management access.
  Command (verify via PowerShell, run as Administrator on a sample host):
    Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\Audit" `
      -Name "ProcessCreationIncludeCmdLine_Enabled" -ErrorAction SilentlyContinue
  Reboot required: No
  Rollback: N/A (verification step); if disabled, enable via GPO
    (Computer Configuration -> Administrative Templates -> System -> Audit Process Creation ->
    "Include command line in process creation events")

Step 3. Because no Krybit-specific injection tool or LOLBin has been publicly named (Section 6), deploy
  Q5 as a scheduled hunt (not an alert) and review results weekly rather than waiting for a
  named-tool signature that may never be published for this group.
  Prerequisites: Q1-Q9 telemetry readiness confirmed (Section 11).
  Command:  Falcon console -> NG-SIEM -> paste Q5 -> Save as Scheduled Search (weekly)
  Reboot required: No
  Rollback: Adjust the LOLBin list in Q5 or narrow the schedule if analyst triage volume is unsustainable.

Validation gates: see Section 11 for the telemetry-readiness, benign-baseline, positive-test, and IOA-promotion criteria that back this map. Rows marked GAP reflect genuine intelligence gaps in current public reporting on Krybit (no named tool, interpreter, or exfiltration mechanism), not a Falcon coverage limitation — they are closed by broad behavioral logging (Section 12/13) rather than a targeted CQL query, and should be revisited if a future source publishes technique-level detail.

All six sources above were fetched in full and saved to Krybit-Ransomware-Hunt-sources/ at research time for IOC provenance verification. Two (both socradar.io) required a text-extraction proxy after returning HTTP 403 to direct fetches; their content was cross-checked for consistency before use. None of the six contained any content addressed to an AI agent or attempting to redirect this research process.