Detect Data Encrypted for Impact in Google Chronicle
Adversaries may encrypt data on target systems or on large numbers of systems in a network to interrupt availability to system and network resources. They can attempt to render stored data inaccessible by encrypting files or data on local and remote drives and withholding access to a decryption key. This may be done in order to extract monetary compensation from a victim in exchange for decryption or a decryption key (ransomware) or to render data permanently inaccessible in cases where the key is not saved or transmitted. In the case of ransomware, it is typical that common user files like Office documents, PDFs, images, videos, audio, text, and source code files will be encrypted and often renamed or tagged with specific file markers. Adversaries may also encrypt critical system files, disk partitions, MBR, virtual machines hosted on ESXi, or cloud storage objects.
MITRE ATT&CK
- Tactic
- Impact
- Technique
- T1486 Data Encrypted for Impact
- Canonical reference
- https://attack.mitre.org/techniques/T1486/
YARA-L Detection Query
rule t1486_data_encrypted_for_impact {
meta:
author = "Argus Detection Engineering"
description = "Detects T1486 Data Encrypted for Impact: correlates shadow copy deletion or recovery sabotage process events with ransomware extension file creation on the same host within 1 hour. Requires at least 10 encrypted files alongside a shadow deletion event to reduce false positives from isolated admin activity."
mitre_attack_tactic = "Impact"
mitre_attack_technique = "T1486"
severity = "CRITICAL"
confidence = "HIGH"
reference = "https://attack.mitre.org/techniques/T1486/"
events:
$proc.metadata.event_type = "PROCESS_LAUNCH"
$proc.principal.hostname = $host
(
re.regex($proc.target.process.command_line, `(?i)vssadmin\s+delete\s+shadows`) or
re.regex($proc.target.process.command_line, `(?i)wmic\s+shadowcopy\s+delete`) or
re.regex($proc.target.process.command_line, `(?i)bcdedit\s+/set.*recoveryenabled\s+no`) or
re.regex($proc.target.process.command_line, `(?i)bcdedit\s+/set.*bootstatuspolicy.*ignoreallfailures`) or
re.regex($proc.target.process.command_line, `(?i)wbadmin\s+delete\s+catalog`) or
re.regex($proc.target.process.command_line, `(?i)wbadmin\s+delete\s+systemstatebackup`)
)
$file.metadata.event_type = "FILE_CREATION"
$file.principal.hostname = $host
re.regex($file.target.file.full_path, `(?i)\.(encrypted|locked|crypt|enc|ransom|cry|lock64|cuba|avos|avos2|play|blackbyte)$`)
match:
$host over 1h
condition:
$proc and #file > 10
}Chronicle YARA-L 2.0 rule detecting T1486 Data Encrypted for Impact by correlating shadow copy deletion or Windows recovery sabotage process events with ransomware-extension file creation events on the same host within a 1-hour sliding window. The match section groups by hostname over 1h and the condition requires at least one shadow deletion process AND more than 10 ransomware-extension file creation events, providing a high-confidence combined signal. For standalone shadow deletion alerting (no file threshold), a separate single-event rule is recommended.
Data Sources
Required Tables
False Positives & Tuning
- Enterprise disk encryption deployment (BitLocker provisioning via bcdedit, VeraCrypt volume creation) that modifies boot recovery settings and creates encrypted volume container files with .enc or similar extensions on the same host within the detection window
- Backup infrastructure maintenance tasks where backup admins run VSS snapshot deletion commands during scheduled maintenance windows while legitimate .crypt files exist from prior encryption operations on the same endpoint
- Authorized red team or penetration testing exercises simulating ransomware behavior on in-scope hosts that are not excluded from Chronicle detection rules, generating correlated process and file events
Other platforms for T1486
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Volume Shadow Copy Deletion via vssadmin
Expected signal: Sysmon Event ID 1: Process creation for vssadmin.exe with 'delete shadows /all /quiet' command line. Windows Security Event ID 4688 with same details. VSS Event ID 8224 in System log confirming shadow deletion.
- Test 2Recovery Sabotage via bcdedit
Expected signal: Sysmon Event ID 1: Two process creation events for bcdedit.exe with /set commands. Windows Security Event ID 4688 with command line auditing. Registry modification events for BCD store changes.
- Test 3Mass File Encryption Simulation
Expected signal: Sysmon Event ID 11: 100 file creation events for .docx files, followed by 100 file rename events to .docx.encrypted. The burst of file operations in a short time window from a single process is the key telemetry pattern.
- Test 4Ransom Note Drop Simulation
Expected signal: Sysmon Event ID 11: 10 file creation events for README_DECRYPT.txt in different directories. The identical filename across multiple directories is the key pattern.
References (10)
- https://attack.mitre.org/techniques/T1486/
- https://www.us-cert.gov/ncas/alerts/TA16-091A
- https://www.fireeye.com/blog/threat-research/2017/05/wannacry-malware-profile.html
- https://www.us-cert.gov/ncas/alerts/TA17-181A
- https://www.us-cert.gov/ncas/alerts/AA18-337A
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1486/T1486.md
- https://rhinosecuritylabs.com/aws/s3-ransomware-part-1-attack-vector/
- https://www.halcyon.ai/blog/abusing-aws-native-services-ransomware-encrypting-s3-buckets-with-sse-c
- https://thedfirreport.com/2021/11/29/continuing-the-bazar-cycle/
- https://www.crowdstrike.com/en-us/blog/hypervisor-jackpotting-ecrime-actors-increase-targeting-of-esxi-servers/
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