This analytic is to look for suspicious raw access read to drive where the master boot record is placed. This technique was seen in several attacks by adversaries or threat actor to wipe, encrypt or overwrite the master boot record code as part of their impact payload. This detection is a good indicator that there is a process try to read or write on MBR sector.
- Type: TTP
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2022-02-17
- Author: Teoderick Contreras, Splunk
- ID: 7b83f666-900c-11ec-a2d9-acde48001122
Kill Chain Phase
- CIS 3
- CIS 5
- CIS 16
1 2 3 4 5 `sysmon` EventCode=9 Device = \\Device\\Harddisk0\\DR0 NOT (Image IN("*\\Windows\\System32\\*", "*\\Windows\\SysWOW64\\*")) | stats count min(_time) as firstTime max(_time) as lastTime by Computer Image Device ProcessGuid ProcessId EventDescription EventCode | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_raw_access_to_master_boot_record_drive_filter`
The SPL above uses the following Macros:
windows_raw_access_to_master_boot_record_drive_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this search, you need to be ingesting logs with the raw access read event (like sysmon eventcode 9), process name and process guid from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.
Known False Positives
This event is really notable but we found minimal number of normal application from system32 folder like svchost.exe accessing it too. In this case we used 'system32' and 'syswow64' path as a filter for this detection.
Associated Analytic Story
|90.0||90||100||process accessing MBR $device$ in $dest$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
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