Agents frequently use possession to move quickly from one location to another. Though the process only takes a brief time, the Agent is vulnerable to attack during this time. The bluepills have no awareness during the possession, and are often confused when they return to consciousness, sometimes badly injured. However, should the Agent "die" while using a possessed bluepill, the bluepill dies as well, with the Agent's RSI disappearing and leaving the bluepill's corpse behind.
After resisting deletion, Agent Smith began to use a method of possession that may have been derived from his old Agent ability to possess bluepills. His method was much more direct; a Smith avatar would force its hand into the RSI of his intended victim, and release a black substance that would slowly overtake the victim RSI and once completely covered, convert the avatar into another Smith.
There were a number of differences between normal possession and Smith's version:
- Smith's version was much slower to act (possibly because he no longer had direct access to the Matrix itself) and was also reversible as long as the victim RSI hasn't been completely covered by the substance.
- Smith could not remotely possess an avatar like normal Agents; he had to be within touching distance to be able to infect other avatars.
- While normal Agent possession can only affect bluepills, Smith's version can affect any and all beings inside the Matrix; other Agents, Exiles, and even redpills. Redpill avatars that have been infected can also return to their host bodies in the Real World, leading to a Smith possessing a human's body.
- A Smith that possesses an Exile with a specific function can utilize that function itself, and may also take on memories and traits of the victim Exile, as seen with the The Oracle's Smith.
- If a single Smith is compromised from within, it can affect every other Smith; as seen when the Machines destroy the Smith occupying Neo's avatar, and every other Smith is destroyed with it.
While never clearly stated, Exile's shells may be possessed bluepills, and the programs must change their shells when they are destroyed. This is seen when the Oracle uses a new body after the Merovingian used kill-codes to her old shell which he acquired in exchange for Sati's exile to the Matrix.