The Secret Agent: A Simple Tale is a 1907 novel by Joseph Conrad, relating a bleak and darkly comic story of spies, terrorists, anarchists and agents provocateurs plotting and counter-plotting in the back streets of London in the early 20th century. It...

Espionage or spying is a practice of gathering intelligence about an organization or a society that is considered secret or confidential without the permission of the holder of the information. It is also the use of spies in a war. Unlike other forms of...

Urban exploration, exploring parts of towns etc which are normally off-limits

In sociology and politics, infiltration may refer to entryism. For example, organization A's members furtively join organization B so that A can try to take over B

InfiltrationMod, a tactical shooter game

Infiltration (hydrology), downward movement of water through soil

Infiltration tactics, tactics developed by the German army in 1917 that broke the trench-warfare stalemate on the western front

Infiltration (medical), the diffusion or accumulation of substances not normal to it or in amounts in excess of the normal

Infiltration (zine), a popular urban exploration zine/website created by Jeff Chapman (a.k.a. Ninjalicious)

Infiltration (HVAC), a heating, ventilation, and air conditioning (HVAC) term for air leakage into buildings

An attempt to sneak across a border, or into a guarded place. See also Palestinian infiltration.

The Transformers: Infiltration, a 2006 comic book series by IDW Publishing