The following analytic identifies the use of curl on Linux or MacOS attempting to download a file from a remote source and pipe it to bash. This is typically found with coinminers and most recently with CVE-2021-44228, a vulnerability in Log4j.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-12-10
- Author: Michael Haag, Splunk
- ID: 900bc324-59f3-11ec-9fb4-acde48001122
|T1105||Ingress Tool Transfer||Command And Control|
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name=curl (Processes.process="*-s *") OR (Processes.process="* |*" AND Processes.process="*bash*") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `curl_download_and_bash_execution_filter`
Associated Analytic Story
How To Implement
To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon for Linux, you will need to ensure mapping is occurring correctly. If the EDR is not parsing the pipe bash in the command-line, modifying the analytic will be required. Add parent process name (Processes.parent_process_name) as needed to filter.
Kill Chain Phase
Known False Positives
False positives should be limited, however filtering may be required.
|80.0||80||100||An instance of $process_name$ was identified on endpoint $dest$ attempting to download a remote file and run it with bash.|
|CVE-2021-44228||Apache Log4j2 2.0-beta9 through 2.15.0 (excluding security releases 2.12.2, 2.12.3, and 2.3.1) JNDI features used in configuration, log messages, and parameters do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who can control log messages or log message parameters can execute arbitrary code loaded from LDAP servers when message lookup substitution is enabled. From log4j 2.15.0, this behavior has been disabled by default. From version 2.16.0 (along with 2.12.2, 2.12.3, and 2.3.1), this functionality has been completely removed. Note that this vulnerability is specific to log4j-core and does not affect log4net, log4cxx, or other Apache Logging Services projects.||9.3|
source | version: 1