it is possible for a legitimate file with these extensions to be created. if this is a true ransomware attack, there will be a large number of files created with these extensions.

Techniques

T1485

Sample rules

Common Ransomware Extensions

source: splunk
technicques:
- T1485

Description

The following analytic detects modifications to files with extensions commonly associated with ransomware. It leverages the Endpoint.Filesystem data model to identify changes in file extensions that match known ransomware patterns. This activity is significant because it suggests an attacker is attempting to encrypt or alter files, potentially leading to severe data loss and operational disruption. If confirmed malicious, this activity could result in the encryption of critical data, rendering it inaccessible and causing significant damage to the organization’s data integrity and availability.

Detection logic


| tstats `security_content_summariesonly` min(_time) as firstTime max(_time) as lastTime count latest(Filesystem.user) as user values(Filesystem.file_path) as file_path from datamodel=Endpoint.Filesystem by Filesystem.file_name Filesystem.dest _time span=1h 
| `drop_dm_object_name(Filesystem)` 
| rex field=file_name "(?<file_extension>\.[^\.]+)$" 
| rex field=file_path "(?<true_file_path>([^\\\]*\\\)*).*" 
| stats min(firstTime) as firstTime max(lastTime) as lastTime latest(user) as user dc(true_file_path) as path_count dc(file_name) as file_count latest(true_file_path) as file_path by dest file_name 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `ransomware_extensions` 
| where path_count > 1 OR file_count > 20 
| `common_ransomware_extensions_filter`