Adversaries may physically introduce computer accessories, networking hardware, or other computing devices into a system or network that can be used as a vector to gain access. Rather than just connecting and distributing payloads via removable storage (i.e. [Replication Through Removable Media](https://attack.mitre.org/techniques/T1091)), more robust hardware additions can be used to introduce new functionalities and/or features into a system that can then be abused.

While public references of usage by threat actors are scarce, many red teams/penetration testers leverage hardware additions for initial access. Commercial and open source products can be leveraged with capabilities such as passive network tapping, network traffic modification (i.e. [Adversary-in-the-Middle](https://attack.mitre.org/techniques/T1557)), keystroke injection, kernel memory reading via DMA, addition of new wireless access points to an existing network, and others.(Citation: Ossmann Star Feb 2011)(Citation: Aleks Weapons Nov 2015)(Citation: Frisk DMA August 2016)(Citation: McMillan Pwn March 2012)