"covert network" is correct and can be used in written English.
It typically refers to a network of people, organizations or activities that are deliberately kept secret or hidden in some way. For example: "The government established a covert network of spies to monitor the activities of foreign countries."
Prosecutors argued that the two ran a large, covert network of paramilitary squads, trained and paid for by Belgrade's Ministry of Interior.
And the N.S.A.'s politics were typical of most of the organizations in the C.I.A.'s covert network: they were socially progressive, anti-colonialist, and sometimes even socialist.
A covert network of secret priests served the spiritual needs of the Catholic gentry and those further down the social scale under their protection.
Soon a covert network of international informants began operating out of the Vatican, secretly denouncing all kinds of Catholic thinkers for modernist leanings.
This and other recent acquittals have effectively absolved Serbia of any responsibility for atrocities committed by proxy armies in Croatia and Bosnia and by the covert network of paramilitary combat units trained, paid and supervised by the secret police.
Such is the dismaying discovery of Honor Bright, a principled English Quaker recently arrived in Ohio, after her new American family admonishes her not to aid the covert network.
They said he had been sent to Dubai last year, provided with a Pakistani passport and told to set up covert networks in India.
Although the wartime plot hinges on a love affair, the technical details of the British-run covert networks and Dutch resistance make for the most absorbing sequences.
His research in wireless networking, cognitive radio networks, cybersecurity, covert networking, and interdisciplinary studies has been funded by the National Science Foundation (NSF), National Institute of Justice (NIJ), NY GRTI and PSC-CUNY.
However, the most powerful and up-to-the-minute rallying appears to have taken place on a more covert social network: BlackBerry Messenger (BBM).
Such a covert affiliation network structure is analyzed by evaluating the one-mode projection of the corresponding hypergraph.
