Adversaries may establish persistence by executing malicious content triggered by hijacked references to Component Object Model (COM) objects. COM is a system within Windows to enable interaction between software components through the operating system.(Citation: Microsoft Component Object Model)  References to various COM objects are stored in the Registry. 

Adversaries can use the COM system to insert malicious code that can be executed in place of legitimate software through hijacking the COM references and relationships as a means for persistence. Hijacking a COM object requires a change in the Registry to replace a reference to a legitimate system component which may cause that component to not work when executed. When that system component is executed through normal system operation the adversary's code will be executed instead.(Citation: GDATA COM Hijacking) An adversary is likely to hijack objects that are used frequently enough to maintain a consistent level of persistence, but are unlikely to break noticeable functionality within the system as to avoid system instability that could lead to detection. 
Component Object Model Hijacking
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1546/015  external_id: T1546.015     source_name: Elastic COM Hijacking  description: Ewing, P. Strom, B. (2016, September 15). How to Hunt: Detecting Persistence & Evasion with the COM. Retrieved September 15, 2016.  url: https://www.elastic.co/blog/how-hunt-detecting-persistence-evasion-com     source_name: GDATA COM Hijacking  description: G DATA. (2014, October). COM Object hijacking: the discreet way of persistence. Retrieved August 13, 2016.  url: https://blog.gdatasoftware.com/2014/10/23941-com-object-hijacking-the-discreet-way-of-persistence     source_name: Microsoft Component Object Model  description: Microsoft. (n.d.). The Component Object Model. Retrieved August 18, 2016.  url: https://msdn.microsoft.com/library/ms694363.aspx     