What does exfiltrate mean?
Exfiltrate is a verb meaning to remove someone or something secretly and illicitly from a place. In its original and still central military sense, it describes withdrawing personnel — often spies, downed pilots, or hostages — from hostile territory by covert means, as when special forces exfiltrate an agent across a border. Since the rise of networked computing, the word has acquired a second, now equally dominant sense: the clandestine transfer of data, files, or classified information out of a computer system or organization, typically by malware or an unauthorized insider. Exfiltration always implies secrecy and wrongdoing; nothing is legitimately exfiltrated. The term pairs naturally with adverbs like "covertly" or "quietly" and appears constantly in intelligence briefings, war reporting, and coverage of cybersecurity breaches. It is the deliberate counterpart of "infiltrate," which describes secret entry rather than secret exit, making the two words a matched pair for describing movement in and out of secured spaces.
verbTo secretly and illicitly remove someone or something from a place, especially to extract a person from a hostile area or to covertly transfer data or classified material out of a secure system or organization.
- (of spies, military forces, etc.) To withdraw or remove (a person) secretly and illicitly from an area, especially a hostile or dangerous one.
- To covertly and illicitly transfer data, files, or other information out of a computer system, network, or organization.
"The operatives exfiltrated the scientist across the border under cover of darkness."
"Special forces worked through the night to exfiltrate the hostage before dawn."
"The malware was designed to quietly exfiltrate customer records to servers overseas."
"Exfiltrate" is the spy world's word for getting people or secrets OUT — the mirror image of "infiltrate," and the verb behind nearly every headline about hackers stealing data.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of exfiltrate
Exfiltrate was formed in English in the mid-twentieth century, evidently modeled on "infiltrate" by replacing the prefix in- ("into") with ex- ("out of"). Both verbs derive ultimately from the medieval Latin filtrum, meaning felt or filtering material, which gave English the noun "filter" and the technical term "filtrate." The word gained currency during Cold War-era military and intelligence operations and was later extended into cybersecurity vocabulary.
Related word forms
How exfiltrate is actually used
The word belongs chiefly to military, intelligence, and cybersecurity registers — formal-to-technical rather than everyday speech. It carries a strongly connotative implication of secrecy and illegitimacy: whatever is exfiltrated is being taken out covertly and without authorization. The data-theft sense has become extremely common since the early 2000s in reporting on hacking and breaches.
Easily confused with exfiltrate
Infiltrate means to secretly enter or gain access to a place or organization, while exfiltrate means to secretly leave or remove something from it.