Not really. Imagine you want to leak a one page printed document. If the covert signal (the employee ID of the leaker) is encoded with tiny dots then it could

Not really. Imagine you want to leak a one page printed document. If the covert signal (the employee ID of the leaker) is encoded with tiny dots then it could be filtered in or out with a band pass filter. Filtering out the data can be done with a fax machine if you can find one. But if the covert data is embedded in the original signal at frequencies close to the signal “frequency” then you don’t stand a chance. The information band of written English provides a huge number of options for hiding other signals: spelling, choice of words, spacing, key phrases, capitalisation, the ordering of items in a list. The government agency from where you are leaking — your adversary — has the original signal from which they adapted your slightly different copy that you leaked. All they have to do is hide 6 to 16 bits of data in 2kb of English language. This is trivial because they have the original plaintext with which to encode and later extract the signal. How do you effectively tackle this, as a leaker? A journalist is the one type of filter capable of obscuring covert traffic at these frequencies. They read the document, summarise the implications, and then write that up. I probably wouldn’t let them keep the original text though.