Techniques
Sample rules
Windows High File Deletion Frequency
- source: splunk
- technicques:
- T1485
Description
The following analytic identifies a high frequency of file deletions by monitoring Sysmon EventCodes 23 and 26 for specific file extensions. This detection leverages Sysmon logs to track deleted target filenames, process names, and process IDs. Such activity is significant as it often indicates ransomware behavior, where files are encrypted and the originals are deleted. If confirmed malicious, this activity could lead to extensive data loss and operational disruption, as ransomware can render critical files inaccessible, demanding a ransom for their recovery.
Detection logic
`sysmon` EventCode IN ("23","26") TargetFilename IN ("*.cmd", "*.ini","*.gif", "*.jpg", "*.jpeg", "*.db", "*.ps1", "*.doc", "*.docx", "*.xls", "*.xlsx", "*.ppt", "*.pptx", "*.bmp","*.zip", "*.rar", "*.7z", "*.chm", "*.png", "*.log", "*.vbs", "*.js", "*.vhd", "*.bak", "*.wbcat", "*.bkf" , "*.backup*", "*.dsk", "*.win") NOT TargetFilename IN ("*\\INetCache\\Content.Outlook\\*")
| stats count min(_time) as firstTime, max(_time) as lastTime values(file_path) as file_path values(file_hash) as file_hash values(file_name) as file_name values(file_modify_time) as file_modify_time values(process_name) as process_name values(process_path) as process_path values(process_guid) as process_guid values(process_id) as process_id values(process_exec) as process_exec by action dest dvc signature signature_id user user_id vendor_product
| where count >=100
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `windows_high_file_deletion_frequency_filter`