Patch System Image
Where this stands
No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.
None of MITRE's analytics for this technique name a log source that maps to a Sigma logsource — they describe abstract data ("Process::None"), API-hook telemetry, or prose channels with no reliable field names behind them.
What the technique is
Adversaries may modify the operating system of a network device to introduce new capabilities or weaken existing defenses. Some network devices are built with a monolithic architecture, where the entire operating system and most of the functionality of the device is contained within a single file. Adversaries may change this file in storage, to be loaded in a future boot, or in memory during runtime. To change the operating system in storage, the adversary will typically use the standard procedures available to device operators. This may involve downloading a new file via typical protocols used on network devices, such as TFTP, FTP, SCP, or a console connection. The original file may be overwritten, or a new file may be written alongside of it and the device reconfigured to boot to the compromised image. To change the operating system in memory, the adversary typically can use one of two methods. In the first, the adversary would make use of native debug commands in the original, unaltered running operating system that allow them to directly modify the relevant memory addresses containing the running operating system. This method typically requires administrative level access to the device. In the second method for changing the operating system in memory, the adversary would make use of the boot loader. […]
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN1293
Defenders may observe adversary attempts to patch system images by monitoring for anomalous file transfers (TFTP, SCP, FTP) of image files, unauthorized CLI commands altering boot system variables, integrity check mismatches between running and baseline OS images, and runtime memory manipulation attempts. Suspicious sequences include uploading a new image, modifying boot parameters, and subsequent reload/reboot of the device. In-memory patching attempts may manifest as debug commands or boot loader manipulation inconsistent with normal administrative activity.
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